[linux.git] / drivers / infiniband / hw / hfi1 / rc.c

/*
 * Copyright(c) 2015, 2016 Intel Corporation.
 *
 * This file is provided under a dual BSD/GPLv2 license.  When using or
 * redistributing this file, you may do so under either license.
 *
 * GPL LICENSE SUMMARY
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of version 2 of the GNU General Public License as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * BSD LICENSE
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *  - Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *  - Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *  - Neither the name of Intel Corporation nor the names of its
 *    contributors may be used to endorse or promote products derived
 *    from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */

#include <linux/io.h>
#include <rdma/rdma_vt.h>
#include <rdma/rdmavt_qp.h>

#include "hfi.h"
#include "qp.h"
#include "verbs_txreq.h"
#include "trace.h"

/* cut down ridiculously long IB macro names */
#define OP(x) RC_OP(x)

/**
 * hfi1_add_retry_timer - add/start a retry timer
 * @qp - the QP
 *
 * add a retry timer on the QP
 */
static inline void hfi1_add_retry_timer(struct rvt_qp *qp)
{
        struct ib_qp *ibqp = &qp->ibqp;
        struct rvt_dev_info *rdi = ib_to_rvt(ibqp->device);

        lockdep_assert_held(&qp->s_lock);
        qp->s_flags |= RVT_S_TIMER;
        /* 4.096 usec. * (1 << qp->timeout) */
        qp->s_timer.expires = jiffies + qp->timeout_jiffies +
                              rdi->busy_jiffies;
        add_timer(&qp->s_timer);
}

/**
 * hfi1_add_rnr_timer - add/start an rnr timer
 * @qp - the QP
 * @to - timeout in usecs
 *
 * add an rnr timer on the QP
 */
void hfi1_add_rnr_timer(struct rvt_qp *qp, u32 to)
{
        struct hfi1_qp_priv *priv = qp->priv;

        lockdep_assert_held(&qp->s_lock);
        qp->s_flags |= RVT_S_WAIT_RNR;
        priv->s_rnr_timer.expires = jiffies + usecs_to_jiffies(to);
        add_timer(&priv->s_rnr_timer);
}

/**
 * hfi1_mod_retry_timer - mod a retry timer
 * @qp - the QP
 *
 * Modify a potentially already running retry
 * timer
 */
static inline void hfi1_mod_retry_timer(struct rvt_qp *qp)
{
        struct ib_qp *ibqp = &qp->ibqp;
        struct rvt_dev_info *rdi = ib_to_rvt(ibqp->device);

        lockdep_assert_held(&qp->s_lock);
        qp->s_flags |= RVT_S_TIMER;
        /* 4.096 usec. * (1 << qp->timeout) */
        mod_timer(&qp->s_timer, jiffies + qp->timeout_jiffies +
                  rdi->busy_jiffies);
}

/**
 * hfi1_stop_retry_timer - stop a retry timer
 * @qp - the QP
 *
 * stop a retry timer and return if the timer
 * had been pending.
 */
static inline int hfi1_stop_retry_timer(struct rvt_qp *qp)
{
        int rval = 0;

        lockdep_assert_held(&qp->s_lock);
        /* Remove QP from retry */
        if (qp->s_flags & RVT_S_TIMER) {
                qp->s_flags &= ~RVT_S_TIMER;
                rval = del_timer(&qp->s_timer);
        }
        return rval;
}

/**
 * hfi1_stop_rc_timers - stop all timers
 * @qp - the QP
 *
 * stop any pending timers
 */
void hfi1_stop_rc_timers(struct rvt_qp *qp)
{
        struct hfi1_qp_priv *priv = qp->priv;

        lockdep_assert_held(&qp->s_lock);
        /* Remove QP from all timers */
        if (qp->s_flags & (RVT_S_TIMER | RVT_S_WAIT_RNR)) {
                qp->s_flags &= ~(RVT_S_TIMER | RVT_S_WAIT_RNR);
                del_timer(&qp->s_timer);
                del_timer(&priv->s_rnr_timer);
        }
}

/**
 * hfi1_stop_rnr_timer - stop an rnr timer
 * @qp - the QP
 *
 * stop an rnr timer and return if the timer
 * had been pending.
 */
static inline int hfi1_stop_rnr_timer(struct rvt_qp *qp)
{
        int rval = 0;
        struct hfi1_qp_priv *priv = qp->priv;

        lockdep_assert_held(&qp->s_lock);
        /* Remove QP from rnr timer */
        if (qp->s_flags & RVT_S_WAIT_RNR) {
                qp->s_flags &= ~RVT_S_WAIT_RNR;
                rval = del_timer(&priv->s_rnr_timer);
        }
        return rval;
}

/**
 * hfi1_del_timers_sync - wait for any timeout routines to exit
 * @qp - the QP
 */
void hfi1_del_timers_sync(struct rvt_qp *qp)
{
        struct hfi1_qp_priv *priv = qp->priv;

        del_timer_sync(&qp->s_timer);
        del_timer_sync(&priv->s_rnr_timer);
}

static u32 restart_sge(struct rvt_sge_state *ss, struct rvt_swqe *wqe,
                       u32 psn, u32 pmtu)
{
        u32 len;

        len = delta_psn(psn, wqe->psn) * pmtu;
        ss->sge = wqe->sg_list[0];
        ss->sg_list = wqe->sg_list + 1;
        ss->num_sge = wqe->wr.num_sge;
        ss->total_len = wqe->length;
        hfi1_skip_sge(ss, len, 0);
        return wqe->length - len;
}

/**
 * make_rc_ack - construct a response packet (ACK, NAK, or RDMA read)
 * @dev: the device for this QP
 * @qp: a pointer to the QP
 * @ohdr: a pointer to the IB header being constructed
 * @ps: the xmit packet state
 *
 * Return 1 if constructed; otherwise, return 0.
 * Note that we are in the responder's side of the QP context.
 * Note the QP s_lock must be held.
 */
static int make_rc_ack(struct hfi1_ibdev *dev, struct rvt_qp *qp,
                       struct ib_other_headers *ohdr,
                       struct hfi1_pkt_state *ps)
{
        struct rvt_ack_entry *e;
        u32 hwords;
        u32 len;
        u32 bth0;
        u32 bth2;
        int middle = 0;
        u32 pmtu = qp->pmtu;
        struct hfi1_qp_priv *priv = qp->priv;

        lockdep_assert_held(&qp->s_lock);
        /* Don't send an ACK if we aren't supposed to. */
        if (!(ib_rvt_state_ops[qp->state] & RVT_PROCESS_RECV_OK))
                goto bail;

        /* header size in 32-bit words LRH+BTH = (8+12)/4. */
        hwords = 5;

        switch (qp->s_ack_state) {
        case OP(RDMA_READ_RESPONSE_LAST):
        case OP(RDMA_READ_RESPONSE_ONLY):
                e = &qp->s_ack_queue[qp->s_tail_ack_queue];
                if (e->rdma_sge.mr) {
                        rvt_put_mr(e->rdma_sge.mr);
                        e->rdma_sge.mr = NULL;
                }
                /* FALLTHROUGH */
        case OP(ATOMIC_ACKNOWLEDGE):
                /*
                 * We can increment the tail pointer now that the last
                 * response has been sent instead of only being
                 * constructed.
                 */
                if (++qp->s_tail_ack_queue > HFI1_MAX_RDMA_ATOMIC)
                        qp->s_tail_ack_queue = 0;
                /* FALLTHROUGH */
        case OP(SEND_ONLY):
        case OP(ACKNOWLEDGE):
                /* Check for no next entry in the queue. */
                if (qp->r_head_ack_queue == qp->s_tail_ack_queue) {
                        if (qp->s_flags & RVT_S_ACK_PENDING)
                                goto normal;
                        goto bail;
                }

                e = &qp->s_ack_queue[qp->s_tail_ack_queue];
                if (e->opcode == OP(RDMA_READ_REQUEST)) {
                        /*
                         * If a RDMA read response is being resent and
                         * we haven't seen the duplicate request yet,
                         * then stop sending the remaining responses the
                         * responder has seen until the requester re-sends it.
                         */
                        len = e->rdma_sge.sge_length;
                        if (len && !e->rdma_sge.mr) {
                                qp->s_tail_ack_queue = qp->r_head_ack_queue;
                                goto bail;
                        }
                        /* Copy SGE state in case we need to resend */
                        ps->s_txreq->mr = e->rdma_sge.mr;
                        if (ps->s_txreq->mr)
                                rvt_get_mr(ps->s_txreq->mr);
                        qp->s_ack_rdma_sge.sge = e->rdma_sge;
                        qp->s_ack_rdma_sge.num_sge = 1;
                        ps->s_txreq->ss = &qp->s_ack_rdma_sge;
                        if (len > pmtu) {
                                len = pmtu;
                                qp->s_ack_state = OP(RDMA_READ_RESPONSE_FIRST);
                        } else {
                                qp->s_ack_state = OP(RDMA_READ_RESPONSE_ONLY);
                                e->sent = 1;
                        }
                        ohdr->u.aeth = hfi1_compute_aeth(qp);
                        hwords++;
                        qp->s_ack_rdma_psn = e->psn;
                        bth2 = mask_psn(qp->s_ack_rdma_psn++);
                } else {
                        /* COMPARE_SWAP or FETCH_ADD */
                        ps->s_txreq->ss = NULL;
                        len = 0;
                        qp->s_ack_state = OP(ATOMIC_ACKNOWLEDGE);
                        ohdr->u.at.aeth = hfi1_compute_aeth(qp);
                        ib_u64_put(e->atomic_data, &ohdr->u.at.atomic_ack_eth);
                        hwords += sizeof(ohdr->u.at) / sizeof(u32);
                        bth2 = mask_psn(e->psn);
                        e->sent = 1;
                }
                bth0 = qp->s_ack_state << 24;
                break;

        case OP(RDMA_READ_RESPONSE_FIRST):
                qp->s_ack_state = OP(RDMA_READ_RESPONSE_MIDDLE);
                /* FALLTHROUGH */
        case OP(RDMA_READ_RESPONSE_MIDDLE):
                ps->s_txreq->ss = &qp->s_ack_rdma_sge;
                ps->s_txreq->mr = qp->s_ack_rdma_sge.sge.mr;
                if (ps->s_txreq->mr)
                        rvt_get_mr(ps->s_txreq->mr);
                len = qp->s_ack_rdma_sge.sge.sge_length;
                if (len > pmtu) {
                        len = pmtu;
                        middle = HFI1_CAP_IS_KSET(SDMA_AHG);
                } else {
                        ohdr->u.aeth = hfi1_compute_aeth(qp);
                        hwords++;
                        qp->s_ack_state = OP(RDMA_READ_RESPONSE_LAST);
                        e = &qp->s_ack_queue[qp->s_tail_ack_queue];
                        e->sent = 1;
                }
                bth0 = qp->s_ack_state << 24;
                bth2 = mask_psn(qp->s_ack_rdma_psn++);
                break;

        default:
normal:
                /*
                 * Send a regular ACK.
                 * Set the s_ack_state so we wait until after sending
                 * the ACK before setting s_ack_state to ACKNOWLEDGE
                 * (see above).
                 */
                qp->s_ack_state = OP(SEND_ONLY);
                qp->s_flags &= ~RVT_S_ACK_PENDING;
                ps->s_txreq->ss = NULL;
                if (qp->s_nak_state)
                        ohdr->u.aeth =
                                cpu_to_be32((qp->r_msn & HFI1_MSN_MASK) |
                                            (qp->s_nak_state <<
                                             HFI1_AETH_CREDIT_SHIFT));
                else
                        ohdr->u.aeth = hfi1_compute_aeth(qp);
                hwords++;
                len = 0;
                bth0 = OP(ACKNOWLEDGE) << 24;
                bth2 = mask_psn(qp->s_ack_psn);
        }
        qp->s_rdma_ack_cnt++;
        qp->s_hdrwords = hwords;
        ps->s_txreq->sde = priv->s_sde;
        ps->s_txreq->s_cur_size = len;
        hfi1_make_ruc_header(qp, ohdr, bth0, bth2, middle, ps);
        /* pbc */
        ps->s_txreq->hdr_dwords = qp->s_hdrwords + 2;
        return 1;

bail:
        qp->s_ack_state = OP(ACKNOWLEDGE);
        /*
         * Ensure s_rdma_ack_cnt changes are committed prior to resetting
         * RVT_S_RESP_PENDING
         */
        smp_wmb();
        qp->s_flags &= ~(RVT_S_RESP_PENDING
                                | RVT_S_ACK_PENDING
                                | RVT_S_AHG_VALID);
        return 0;
}

/**
 * hfi1_make_rc_req - construct a request packet (SEND, RDMA r/w, ATOMIC)
 * @qp: a pointer to the QP
 *
 * Assumes s_lock is held.
 *
 * Return 1 if constructed; otherwise, return 0.
 */
int hfi1_make_rc_req(struct rvt_qp *qp, struct hfi1_pkt_state *ps)
{
        struct hfi1_qp_priv *priv = qp->priv;
        struct hfi1_ibdev *dev = to_idev(qp->ibqp.device);
        struct ib_other_headers *ohdr;
        struct rvt_sge_state *ss;
        struct rvt_swqe *wqe;
        /* header size in 32-bit words LRH+BTH = (8+12)/4. */
        u32 hwords = 5;
        u32 len;
        u32 bth0 = 0;
        u32 bth2;
        u32 pmtu = qp->pmtu;
        char newreq;
        int middle = 0;
        int delta;

        lockdep_assert_held(&qp->s_lock);
        ps->s_txreq = get_txreq(ps->dev, qp);
        if (IS_ERR(ps->s_txreq))
                goto bail_no_tx;

        ohdr = &ps->s_txreq->phdr.hdr.u.oth;
        if (qp->remote_ah_attr.ah_flags & IB_AH_GRH)
                ohdr = &ps->s_txreq->phdr.hdr.u.l.oth;

        /* Sending responses has higher priority over sending requests. */
        if ((qp->s_flags & RVT_S_RESP_PENDING) &&
            make_rc_ack(dev, qp, ohdr, ps))
                return 1;

        if (!(ib_rvt_state_ops[qp->state] & RVT_PROCESS_SEND_OK)) {
                if (!(ib_rvt_state_ops[qp->state] & RVT_FLUSH_SEND))
                        goto bail;
                /* We are in the error state, flush the work request. */
                smp_read_barrier_depends(); /* see post_one_send() */
                if (qp->s_last == READ_ONCE(qp->s_head))
                        goto bail;
                /* If DMAs are in progress, we can't flush immediately. */
                if (iowait_sdma_pending(&priv->s_iowait)) {
                        qp->s_flags |= RVT_S_WAIT_DMA;
                        goto bail;
                }
                clear_ahg(qp);
                wqe = rvt_get_swqe_ptr(qp, qp->s_last);
                hfi1_send_complete(qp, wqe, qp->s_last != qp->s_acked ?
                        IB_WC_SUCCESS : IB_WC_WR_FLUSH_ERR);
                /* will get called again */
                goto done_free_tx;
        }

        if (qp->s_flags & (RVT_S_WAIT_RNR | RVT_S_WAIT_ACK))
                goto bail;

        if (cmp_psn(qp->s_psn, qp->s_sending_hpsn) <= 0) {
                if (cmp_psn(qp->s_sending_psn, qp->s_sending_hpsn) <= 0) {
                        qp->s_flags |= RVT_S_WAIT_PSN;
                        goto bail;
                }
                qp->s_sending_psn = qp->s_psn;
                qp->s_sending_hpsn = qp->s_psn - 1;
        }

        /* Send a request. */
        wqe = rvt_get_swqe_ptr(qp, qp->s_cur);
        switch (qp->s_state) {
        default:
                if (!(ib_rvt_state_ops[qp->state] & RVT_PROCESS_NEXT_SEND_OK))
                        goto bail;
                /*
                 * Resend an old request or start a new one.
                 *
                 * We keep track of the current SWQE so that
                 * we don't reset the "furthest progress" state
                 * if we need to back up.
                 */
                newreq = 0;
                if (qp->s_cur == qp->s_tail) {
                        /* Check if send work queue is empty. */
                        smp_read_barrier_depends(); /* see post_one_send() */
                        if (qp->s_tail == READ_ONCE(qp->s_head)) {
                                clear_ahg(qp);
                                goto bail;
                        }
                        /*
                         * If a fence is requested, wait for previous
                         * RDMA read and atomic operations to finish.
                         */
                        if ((wqe->wr.send_flags & IB_SEND_FENCE) &&
                            qp->s_num_rd_atomic) {
                                qp->s_flags |= RVT_S_WAIT_FENCE;
                                goto bail;
                        }
                        /*
                         * Local operations are processed immediately
                         * after all prior requests have completed
                         */
                        if (wqe->wr.opcode == IB_WR_REG_MR ||
                            wqe->wr.opcode == IB_WR_LOCAL_INV) {
                                int local_ops = 0;
                                int err = 0;

                                if (qp->s_last != qp->s_cur)
                                        goto bail;
                                if (++qp->s_cur == qp->s_size)
                                        qp->s_cur = 0;
                                if (++qp->s_tail == qp->s_size)
                                        qp->s_tail = 0;
                                if (!(wqe->wr.send_flags &
                                      RVT_SEND_COMPLETION_ONLY)) {
                                        err = rvt_invalidate_rkey(
                                                qp,
                                                wqe->wr.ex.invalidate_rkey);
                                        local_ops = 1;
                                }
                                hfi1_send_complete(qp, wqe,
                                                   err ? IB_WC_LOC_PROT_ERR
                                                       : IB_WC_SUCCESS);
                                if (local_ops)
                                        atomic_dec(&qp->local_ops_pending);
                                qp->s_hdrwords = 0;
                                goto done_free_tx;
                        }

                        newreq = 1;
                        qp->s_psn = wqe->psn;
                }
                /*
                 * Note that we have to be careful not to modify the
                 * original work request since we may need to resend
                 * it.
                 */
                len = wqe->length;
                ss = &qp->s_sge;
                bth2 = mask_psn(qp->s_psn);
                switch (wqe->wr.opcode) {
                case IB_WR_SEND:
                case IB_WR_SEND_WITH_IMM:
                case IB_WR_SEND_WITH_INV:
                        /* If no credit, return. */
                        if (!(qp->s_flags & RVT_S_UNLIMITED_CREDIT) &&
                            cmp_msn(wqe->ssn, qp->s_lsn + 1) > 0) {
                                qp->s_flags |= RVT_S_WAIT_SSN_CREDIT;
                                goto bail;
                        }
                        if (len > pmtu) {
                                qp->s_state = OP(SEND_FIRST);
                                len = pmtu;
                                break;
                        }
                        if (wqe->wr.opcode == IB_WR_SEND) {
                                qp->s_state = OP(SEND_ONLY);
                        } else if (wqe->wr.opcode == IB_WR_SEND_WITH_IMM) {
                                qp->s_state = OP(SEND_ONLY_WITH_IMMEDIATE);
                                /* Immediate data comes after the BTH */
                                ohdr->u.imm_data = wqe->wr.ex.imm_data;
                                hwords += 1;
                        } else {
                                qp->s_state = OP(SEND_ONLY_WITH_INVALIDATE);
                                /* Invalidate rkey comes after the BTH */
                                ohdr->u.ieth = cpu_to_be32(
                                                wqe->wr.ex.invalidate_rkey);
                                hwords += 1;
                        }
                        if (wqe->wr.send_flags & IB_SEND_SOLICITED)
                                bth0 |= IB_BTH_SOLICITED;
                        bth2 |= IB_BTH_REQ_ACK;
                        if (++qp->s_cur == qp->s_size)
                                qp->s_cur = 0;
                        break;

                case IB_WR_RDMA_WRITE:
                        if (newreq && !(qp->s_flags & RVT_S_UNLIMITED_CREDIT))
                                qp->s_lsn++;
                        /* FALLTHROUGH */
                case IB_WR_RDMA_WRITE_WITH_IMM:
                        /* If no credit, return. */
                        if (!(qp->s_flags & RVT_S_UNLIMITED_CREDIT) &&
                            cmp_msn(wqe->ssn, qp->s_lsn + 1) > 0) {
                                qp->s_flags |= RVT_S_WAIT_SSN_CREDIT;
                                goto bail;
                        }
                        put_ib_reth_vaddr(
                                wqe->rdma_wr.remote_addr,
                                &ohdr->u.rc.reth);
                        ohdr->u.rc.reth.rkey =
                                cpu_to_be32(wqe->rdma_wr.rkey);
                        ohdr->u.rc.reth.length = cpu_to_be32(len);
                        hwords += sizeof(struct ib_reth) / sizeof(u32);
                        if (len > pmtu) {
                                qp->s_state = OP(RDMA_WRITE_FIRST);
                                len = pmtu;
                                break;
                        }
                        if (wqe->wr.opcode == IB_WR_RDMA_WRITE) {
                                qp->s_state = OP(RDMA_WRITE_ONLY);
                        } else {
                                qp->s_state =
                                        OP(RDMA_WRITE_ONLY_WITH_IMMEDIATE);
                                /* Immediate data comes after RETH */
                                ohdr->u.rc.imm_data = wqe->wr.ex.imm_data;
                                hwords += 1;
                                if (wqe->wr.send_flags & IB_SEND_SOLICITED)
                                        bth0 |= IB_BTH_SOLICITED;
                        }
                        bth2 |= IB_BTH_REQ_ACK;
                        if (++qp->s_cur == qp->s_size)
                                qp->s_cur = 0;
                        break;

                case IB_WR_RDMA_READ:
                        /*
                         * Don't allow more operations to be started
                         * than the QP limits allow.
                         */
                        if (newreq) {
                                if (qp->s_num_rd_atomic >=
                                    qp->s_max_rd_atomic) {
                                        qp->s_flags |= RVT_S_WAIT_RDMAR;
                                        goto bail;
                                }
                                qp->s_num_rd_atomic++;
                                if (!(qp->s_flags & RVT_S_UNLIMITED_CREDIT))
                                        qp->s_lsn++;
                        }
                        put_ib_reth_vaddr(
                                wqe->rdma_wr.remote_addr,
                                &ohdr->u.rc.reth);
                        ohdr->u.rc.reth.rkey =
                                cpu_to_be32(wqe->rdma_wr.rkey);
                        ohdr->u.rc.reth.length = cpu_to_be32(len);
                        qp->s_state = OP(RDMA_READ_REQUEST);
                        hwords += sizeof(ohdr->u.rc.reth) / sizeof(u32);
                        ss = NULL;
                        len = 0;
                        bth2 |= IB_BTH_REQ_ACK;
                        if (++qp->s_cur == qp->s_size)
                                qp->s_cur = 0;
                        break;

                case IB_WR_ATOMIC_CMP_AND_SWP:
                case IB_WR_ATOMIC_FETCH_AND_ADD:
                        /*
                         * Don't allow more operations to be started
                         * than the QP limits allow.
                         */
                        if (newreq) {
                                if (qp->s_num_rd_atomic >=
                                    qp->s_max_rd_atomic) {
                                        qp->s_flags |= RVT_S_WAIT_RDMAR;
                                        goto bail;
                                }
                                qp->s_num_rd_atomic++;
                                if (!(qp->s_flags & RVT_S_UNLIMITED_CREDIT))
                                        qp->s_lsn++;
                        }
                        if (wqe->wr.opcode == IB_WR_ATOMIC_CMP_AND_SWP) {
                                qp->s_state = OP(COMPARE_SWAP);
                                put_ib_ateth_swap(wqe->atomic_wr.swap,
                                                  &ohdr->u.atomic_eth);
                                put_ib_ateth_compare(wqe->atomic_wr.compare_add,
                                                     &ohdr->u.atomic_eth);
                        } else {
                                qp->s_state = OP(FETCH_ADD);
                                put_ib_ateth_swap(wqe->atomic_wr.compare_add,
                                                  &ohdr->u.atomic_eth);
                                put_ib_ateth_compare(0, &ohdr->u.atomic_eth);
                        }
                        put_ib_ateth_vaddr(wqe->atomic_wr.remote_addr,
                                           &ohdr->u.atomic_eth);
                        ohdr->u.atomic_eth.rkey = cpu_to_be32(
                                wqe->atomic_wr.rkey);
                        hwords += sizeof(struct ib_atomic_eth) / sizeof(u32);
                        ss = NULL;
                        len = 0;
                        bth2 |= IB_BTH_REQ_ACK;
                        if (++qp->s_cur == qp->s_size)
                                qp->s_cur = 0;
                        break;

                default:
                        goto bail;
                }
                qp->s_sge.sge = wqe->sg_list[0];
                qp->s_sge.sg_list = wqe->sg_list + 1;
                qp->s_sge.num_sge = wqe->wr.num_sge;
                qp->s_sge.total_len = wqe->length;
                qp->s_len = wqe->length;
                if (newreq) {
                        qp->s_tail++;
                        if (qp->s_tail >= qp->s_size)
                                qp->s_tail = 0;
                }
                if (wqe->wr.opcode == IB_WR_RDMA_READ)
                        qp->s_psn = wqe->lpsn + 1;
                else
                        qp->s_psn++;
                break;

        case OP(RDMA_READ_RESPONSE_FIRST):
                /*
                 * qp->s_state is normally set to the opcode of the
                 * last packet constructed for new requests and therefore
                 * is never set to RDMA read response.
                 * RDMA_READ_RESPONSE_FIRST is used by the ACK processing
                 * thread to indicate a SEND needs to be restarted from an
                 * earlier PSN without interfering with the sending thread.
                 * See restart_rc().
                 */
                qp->s_len = restart_sge(&qp->s_sge, wqe, qp->s_psn, pmtu);
                /* FALLTHROUGH */
        case OP(SEND_FIRST):
                qp->s_state = OP(SEND_MIDDLE);
                /* FALLTHROUGH */
        case OP(SEND_MIDDLE):
                bth2 = mask_psn(qp->s_psn++);
                ss = &qp->s_sge;
                len = qp->s_len;
                if (len > pmtu) {
                        len = pmtu;
                        middle = HFI1_CAP_IS_KSET(SDMA_AHG);
                        break;
                }
                if (wqe->wr.opcode == IB_WR_SEND) {
                        qp->s_state = OP(SEND_LAST);
                } else if (wqe->wr.opcode == IB_WR_SEND_WITH_IMM) {
                        qp->s_state = OP(SEND_LAST_WITH_IMMEDIATE);
                        /* Immediate data comes after the BTH */
                        ohdr->u.imm_data = wqe->wr.ex.imm_data;
                        hwords += 1;
                } else {
                        qp->s_state = OP(SEND_LAST_WITH_INVALIDATE);
                        /* invalidate data comes after the BTH */
                        ohdr->u.ieth = cpu_to_be32(wqe->wr.ex.invalidate_rkey);
                        hwords += 1;
                }
                if (wqe->wr.send_flags & IB_SEND_SOLICITED)
                        bth0 |= IB_BTH_SOLICITED;
                bth2 |= IB_BTH_REQ_ACK;
                qp->s_cur++;
                if (qp->s_cur >= qp->s_size)
                        qp->s_cur = 0;
                break;

        case OP(RDMA_READ_RESPONSE_LAST):
                /*
                 * qp->s_state is normally set to the opcode of the
                 * last packet constructed for new requests and therefore
                 * is never set to RDMA read response.
                 * RDMA_READ_RESPONSE_LAST is used by the ACK processing
                 * thread to indicate a RDMA write needs to be restarted from
                 * an earlier PSN without interfering with the sending thread.
                 * See restart_rc().
                 */
                qp->s_len = restart_sge(&qp->s_sge, wqe, qp->s_psn, pmtu);
                /* FALLTHROUGH */
        case OP(RDMA_WRITE_FIRST):
                qp->s_state = OP(RDMA_WRITE_MIDDLE);
                /* FALLTHROUGH */
        case OP(RDMA_WRITE_MIDDLE):
                bth2 = mask_psn(qp->s_psn++);
                ss = &qp->s_sge;
                len = qp->s_len;
                if (len > pmtu) {
                        len = pmtu;
                        middle = HFI1_CAP_IS_KSET(SDMA_AHG);
                        break;
                }
                if (wqe->wr.opcode == IB_WR_RDMA_WRITE) {
                        qp->s_state = OP(RDMA_WRITE_LAST);
                } else {
                        qp->s_state = OP(RDMA_WRITE_LAST_WITH_IMMEDIATE);
                        /* Immediate data comes after the BTH */
                        ohdr->u.imm_data = wqe->wr.ex.imm_data;
                        hwords += 1;
                        if (wqe->wr.send_flags & IB_SEND_SOLICITED)
                                bth0 |= IB_BTH_SOLICITED;
                }
                bth2 |= IB_BTH_REQ_ACK;
                qp->s_cur++;
                if (qp->s_cur >= qp->s_size)
                        qp->s_cur = 0;
                break;

        case OP(RDMA_READ_RESPONSE_MIDDLE):
                /*
                 * qp->s_state is normally set to the opcode of the
                 * last packet constructed for new requests and therefore
                 * is never set to RDMA read response.
                 * RDMA_READ_RESPONSE_MIDDLE is used by the ACK processing
                 * thread to indicate a RDMA read needs to be restarted from
                 * an earlier PSN without interfering with the sending thread.
                 * See restart_rc().
                 */
                len = (delta_psn(qp->s_psn, wqe->psn)) * pmtu;
                put_ib_reth_vaddr(
                        wqe->rdma_wr.remote_addr + len,
                        &ohdr->u.rc.reth);
                ohdr->u.rc.reth.rkey =
                        cpu_to_be32(wqe->rdma_wr.rkey);
                ohdr->u.rc.reth.length = cpu_to_be32(wqe->length - len);
                qp->s_state = OP(RDMA_READ_REQUEST);
                hwords += sizeof(ohdr->u.rc.reth) / sizeof(u32);
                bth2 = mask_psn(qp->s_psn) | IB_BTH_REQ_ACK;
                qp->s_psn = wqe->lpsn + 1;
                ss = NULL;
                len = 0;
                qp->s_cur++;
                if (qp->s_cur == qp->s_size)
                        qp->s_cur = 0;
                break;
        }
        qp->s_sending_hpsn = bth2;
        delta = delta_psn(bth2, wqe->psn);
        if (delta && delta % HFI1_PSN_CREDIT == 0)
                bth2 |= IB_BTH_REQ_ACK;
        if (qp->s_flags & RVT_S_SEND_ONE) {
                qp->s_flags &= ~RVT_S_SEND_ONE;
                qp->s_flags |= RVT_S_WAIT_ACK;
                bth2 |= IB_BTH_REQ_ACK;
        }
        qp->s_len -= len;
        qp->s_hdrwords = hwords;
        ps->s_txreq->sde = priv->s_sde;
        ps->s_txreq->ss = ss;
        ps->s_txreq->s_cur_size = len;
        hfi1_make_ruc_header(
                qp,
                ohdr,
                bth0 | (qp->s_state << 24),
                bth2,
                middle,
                ps);
        /* pbc */
        ps->s_txreq->hdr_dwords = qp->s_hdrwords + 2;
        return 1;

done_free_tx:
        hfi1_put_txreq(ps->s_txreq);
        ps->s_txreq = NULL;
        return 1;

bail:
        hfi1_put_txreq(ps->s_txreq);

bail_no_tx:
        ps->s_txreq = NULL;
        qp->s_flags &= ~RVT_S_BUSY;
        qp->s_hdrwords = 0;
        return 0;
}

/**
 * hfi1_send_rc_ack - Construct an ACK packet and send it
 * @qp: a pointer to the QP
 *
 * This is called from hfi1_rc_rcv() and handle_receive_interrupt().
 * Note that RDMA reads and atomics are handled in the
 * send side QP state and send engine.
 */
void hfi1_send_rc_ack(struct hfi1_ctxtdata *rcd, struct rvt_qp *qp,
                      int is_fecn)
{
        struct hfi1_ibport *ibp = rcd_to_iport(rcd);
        struct hfi1_pportdata *ppd = ppd_from_ibp(ibp);
        u64 pbc, pbc_flags = 0;
        u16 lrh0;
        u16 sc5;
        u32 bth0;
        u32 hwords;
        u32 vl, plen;
        struct send_context *sc;
        struct pio_buf *pbuf;
        struct ib_header hdr;
        struct ib_other_headers *ohdr;
        unsigned long flags;
        struct hfi1_qp_priv *priv = qp->priv;

        /* clear the defer count */
        priv->r_adefered = 0;

        /* Don't send ACK or NAK if a RDMA read or atomic is pending. */
        if (qp->s_flags & RVT_S_RESP_PENDING)
                goto queue_ack;

        /* Ensure s_rdma_ack_cnt changes are committed */
        smp_read_barrier_depends();
        if (qp->s_rdma_ack_cnt)
                goto queue_ack;

        /* Construct the header */
        /* header size in 32-bit words LRH+BTH+AETH = (8+12+4)/4 */
        hwords = 6;
        if (unlikely(qp->remote_ah_attr.ah_flags & IB_AH_GRH)) {
                hwords += hfi1_make_grh(ibp, &hdr.u.l.grh,
                                       &qp->remote_ah_attr.grh, hwords, 0);
                ohdr = &hdr.u.l.oth;
                lrh0 = HFI1_LRH_GRH;
        } else {
                ohdr = &hdr.u.oth;
                lrh0 = HFI1_LRH_BTH;
        }
        /* read pkey_index w/o lock (its atomic) */
        bth0 = hfi1_get_pkey(ibp, qp->s_pkey_index) | (OP(ACKNOWLEDGE) << 24);
        if (qp->s_mig_state == IB_MIG_MIGRATED)
                bth0 |= IB_BTH_MIG_REQ;
        if (qp->r_nak_state)
                ohdr->u.aeth = cpu_to_be32((qp->r_msn & HFI1_MSN_MASK) |
                                            (qp->r_nak_state <<
                                             HFI1_AETH_CREDIT_SHIFT));
        else
                ohdr->u.aeth = hfi1_compute_aeth(qp);
        sc5 = ibp->sl_to_sc[qp->remote_ah_attr.sl];
        /* set PBC_DC_INFO bit (aka SC[4]) in pbc_flags */
        pbc_flags |= ((!!(sc5 & 0x10)) << PBC_DC_INFO_SHIFT);
        lrh0 |= (sc5 & 0xf) << 12 | (qp->remote_ah_attr.sl & 0xf) << 4;
        hdr.lrh[0] = cpu_to_be16(lrh0);
        hdr.lrh[1] = cpu_to_be16(qp->remote_ah_attr.dlid);
        hdr.lrh[2] = cpu_to_be16(hwords + SIZE_OF_CRC);
        hdr.lrh[3] = cpu_to_be16(ppd->lid | qp->remote_ah_attr.src_path_bits);
        ohdr->bth[0] = cpu_to_be32(bth0);
        ohdr->bth[1] = cpu_to_be32(qp->remote_qpn);
        ohdr->bth[1] |= cpu_to_be32((!!is_fecn) << HFI1_BECN_SHIFT);
        ohdr->bth[2] = cpu_to_be32(mask_psn(qp->r_ack_psn));

        /* Don't try to send ACKs if the link isn't ACTIVE */
        if (driver_lstate(ppd) != IB_PORT_ACTIVE)
                return;

        sc = rcd->sc;
        plen = 2 /* PBC */ + hwords;
        vl = sc_to_vlt(ppd->dd, sc5);
        pbc = create_pbc(ppd, pbc_flags, qp->srate_mbps, vl, plen);

        pbuf = sc_buffer_alloc(sc, plen, NULL, NULL);
        if (!pbuf) {
                /*
                 * We have no room to send at the moment.  Pass
                 * responsibility for sending the ACK to the send engine
                 * so that when enough buffer space becomes available,
                 * the ACK is sent ahead of other outgoing packets.
                 */
                goto queue_ack;
        }

        trace_ack_output_ibhdr(dd_from_ibdev(qp->ibqp.device), &hdr);

        /* write the pbc and data */
        ppd->dd->pio_inline_send(ppd->dd, pbuf, pbc, &hdr, hwords);

        return;

queue_ack:
        spin_lock_irqsave(&qp->s_lock, flags);
        if (!(ib_rvt_state_ops[qp->state] & RVT_PROCESS_RECV_OK))
                goto unlock;
        this_cpu_inc(*ibp->rvp.rc_qacks);
        qp->s_flags |= RVT_S_ACK_PENDING | RVT_S_RESP_PENDING;
        qp->s_nak_state = qp->r_nak_state;
        qp->s_ack_psn = qp->r_ack_psn;
        if (is_fecn)
                qp->s_flags |= RVT_S_ECN;

        /* Schedule the send engine. */
        hfi1_schedule_send(qp);
unlock:
        spin_unlock_irqrestore(&qp->s_lock, flags);
}

/**
 * reset_psn - reset the QP state to send starting from PSN
 * @qp: the QP
 * @psn: the packet sequence number to restart at
 *
 * This is called from hfi1_rc_rcv() to process an incoming RC ACK
 * for the given QP.
 * Called at interrupt level with the QP s_lock held.
 */
static void reset_psn(struct rvt_qp *qp, u32 psn)
{
        u32 n = qp->s_acked;
        struct rvt_swqe *wqe = rvt_get_swqe_ptr(qp, n);
        u32 opcode;

        lockdep_assert_held(&qp->s_lock);
        qp->s_cur = n;

        /*
         * If we are starting the request from the beginning,
         * let the normal send code handle initialization.
         */
        if (cmp_psn(psn, wqe->psn) <= 0) {
                qp->s_state = OP(SEND_LAST);
                goto done;
        }

        /* Find the work request opcode corresponding to the given PSN. */
        opcode = wqe->wr.opcode;
        for (;;) {
                int diff;

                if (++n == qp->s_size)
                        n = 0;
                if (n == qp->s_tail)
                        break;
                wqe = rvt_get_swqe_ptr(qp, n);
                diff = cmp_psn(psn, wqe->psn);
                if (diff < 0)
                        break;
                qp->s_cur = n;
                /*
                 * If we are starting the request from the beginning,
                 * let the normal send code handle initialization.
                 */
                if (diff == 0) {
                        qp->s_state = OP(SEND_LAST);
                        goto done;
                }
                opcode = wqe->wr.opcode;
        }

        /*
         * Set the state to restart in the middle of a request.
         * Don't change the s_sge, s_cur_sge, or s_cur_size.
         * See hfi1_make_rc_req().
         */
        switch (opcode) {
        case IB_WR_SEND:
        case IB_WR_SEND_WITH_IMM:
                qp->s_state = OP(RDMA_READ_RESPONSE_FIRST);
                break;

        case IB_WR_RDMA_WRITE:
        case IB_WR_RDMA_WRITE_WITH_IMM:
                qp->s_state = OP(RDMA_READ_RESPONSE_LAST);
                break;

        case IB_WR_RDMA_READ:
                qp->s_state = OP(RDMA_READ_RESPONSE_MIDDLE);
                break;

        default:
                /*
                 * This case shouldn't happen since its only
                 * one PSN per req.
                 */
                qp->s_state = OP(SEND_LAST);
        }
done:
        qp->s_psn = psn;
        /*
         * Set RVT_S_WAIT_PSN as rc_complete() may start the timer
         * asynchronously before the send engine can get scheduled.
         * Doing it in hfi1_make_rc_req() is too late.
         */
        if ((cmp_psn(qp->s_psn, qp->s_sending_hpsn) <= 0) &&
            (cmp_psn(qp->s_sending_psn, qp->s_sending_hpsn) <= 0))
                qp->s_flags |= RVT_S_WAIT_PSN;
        qp->s_flags &= ~RVT_S_AHG_VALID;
}

/*
 * Back up requester to resend the last un-ACKed request.
 * The QP r_lock and s_lock should be held and interrupts disabled.
 */
static void restart_rc(struct rvt_qp *qp, u32 psn, int wait)
{
        struct rvt_swqe *wqe = rvt_get_swqe_ptr(qp, qp->s_acked);
        struct hfi1_ibport *ibp;

        lockdep_assert_held(&qp->r_lock);
        lockdep_assert_held(&qp->s_lock);
        if (qp->s_retry == 0) {
                if (qp->s_mig_state == IB_MIG_ARMED) {
                        hfi1_migrate_qp(qp);
                        qp->s_retry = qp->s_retry_cnt;
                } else if (qp->s_last == qp->s_acked) {
                        hfi1_send_complete(qp, wqe, IB_WC_RETRY_EXC_ERR);
                        rvt_error_qp(qp, IB_WC_WR_FLUSH_ERR);
                        return;
                } else { /* need to handle delayed completion */
                        return;
                }
        } else {
                qp->s_retry--;
        }

        ibp = to_iport(qp->ibqp.device, qp->port_num);
        if (wqe->wr.opcode == IB_WR_RDMA_READ)
                ibp->rvp.n_rc_resends++;
        else
                ibp->rvp.n_rc_resends += delta_psn(qp->s_psn, psn);

        qp->s_flags &= ~(RVT_S_WAIT_FENCE | RVT_S_WAIT_RDMAR |
                         RVT_S_WAIT_SSN_CREDIT | RVT_S_WAIT_PSN |
                         RVT_S_WAIT_ACK);
        if (wait)
                qp->s_flags |= RVT_S_SEND_ONE;
        reset_psn(qp, psn);
}

/*
 * This is called from s_timer for missing responses.
 */
void hfi1_rc_timeout(unsigned long arg)
{
        struct rvt_qp *qp = (struct rvt_qp *)arg;
        struct hfi1_ibport *ibp;
        unsigned long flags;

        spin_lock_irqsave(&qp->r_lock, flags);
        spin_lock(&qp->s_lock);
        if (qp->s_flags & RVT_S_TIMER) {
                ibp = to_iport(qp->ibqp.device, qp->port_num);
                ibp->rvp.n_rc_timeouts++;
                qp->s_flags &= ~RVT_S_TIMER;
                del_timer(&qp->s_timer);
                trace_hfi1_timeout(qp, qp->s_last_psn + 1);
                restart_rc(qp, qp->s_last_psn + 1, 1);
                hfi1_schedule_send(qp);
        }
        spin_unlock(&qp->s_lock);
        spin_unlock_irqrestore(&qp->r_lock, flags);
}

/*
 * This is called from s_timer for RNR timeouts.
 */
void hfi1_rc_rnr_retry(unsigned long arg)
{
        struct rvt_qp *qp = (struct rvt_qp *)arg;
        unsigned long flags;

        spin_lock_irqsave(&qp->s_lock, flags);
        hfi1_stop_rnr_timer(qp);
        hfi1_schedule_send(qp);
        spin_unlock_irqrestore(&qp->s_lock, flags);
}

/*
 * Set qp->s_sending_psn to the next PSN after the given one.
 * This would be psn+1 except when RDMA reads are present.
 */
static void reset_sending_psn(struct rvt_qp *qp, u32 psn)
{
        struct rvt_swqe *wqe;
        u32 n = qp->s_last;

        lockdep_assert_held(&qp->s_lock);
        /* Find the work request corresponding to the given PSN. */
        for (;;) {
                wqe = rvt_get_swqe_ptr(qp, n);
                if (cmp_psn(psn, wqe->lpsn) <= 0) {
                        if (wqe->wr.opcode == IB_WR_RDMA_READ)
                                qp->s_sending_psn = wqe->lpsn + 1;
                        else
                                qp->s_sending_psn = psn + 1;
                        break;
                }
                if (++n == qp->s_size)
                        n = 0;
                if (n == qp->s_tail)
                        break;
        }
}

/*
 * This should be called with the QP s_lock held and interrupts disabled.
 */
void hfi1_rc_send_complete(struct rvt_qp *qp, struct ib_header *hdr)
{
        struct ib_other_headers *ohdr;
        struct rvt_swqe *wqe;
        u32 opcode;
        u32 psn;

        lockdep_assert_held(&qp->s_lock);
        if (!(ib_rvt_state_ops[qp->state] & RVT_PROCESS_OR_FLUSH_SEND))
                return;

        /* Find out where the BTH is */
        if ((be16_to_cpu(hdr->lrh[0]) & 3) == HFI1_LRH_BTH)
                ohdr = &hdr->u.oth;
        else
                ohdr = &hdr->u.l.oth;

        opcode = be32_to_cpu(ohdr->bth[0]) >> 24;
        if (opcode >= OP(RDMA_READ_RESPONSE_FIRST) &&
            opcode <= OP(ATOMIC_ACKNOWLEDGE)) {
                WARN_ON(!qp->s_rdma_ack_cnt);
                qp->s_rdma_ack_cnt--;
                return;
        }

        psn = be32_to_cpu(ohdr->bth[2]);
        reset_sending_psn(qp, psn);

        /*
         * Start timer after a packet requesting an ACK has been sent and
         * there are still requests that haven't been acked.
         */
        if ((psn & IB_BTH_REQ_ACK) && qp->s_acked != qp->s_tail &&
            !(qp->s_flags &
                (RVT_S_TIMER | RVT_S_WAIT_RNR | RVT_S_WAIT_PSN)) &&
                (ib_rvt_state_ops[qp->state] & RVT_PROCESS_RECV_OK))
                hfi1_add_retry_timer(qp);

        while (qp->s_last != qp->s_acked) {
                u32 s_last;

                wqe = rvt_get_swqe_ptr(qp, qp->s_last);
                if (cmp_psn(wqe->lpsn, qp->s_sending_psn) >= 0 &&
                    cmp_psn(qp->s_sending_psn, qp->s_sending_hpsn) <= 0)
                        break;
                s_last = qp->s_last;
                if (++s_last >= qp->s_size)
                        s_last = 0;
                qp->s_last = s_last;
                /* see post_send() */
                barrier();
                rvt_put_swqe(wqe);
                rvt_qp_swqe_complete(qp, wqe, IB_WC_SUCCESS);
        }
        /*
         * If we were waiting for sends to complete before re-sending,
         * and they are now complete, restart sending.
         */
        trace_hfi1_sendcomplete(qp, psn);
        if (qp->s_flags & RVT_S_WAIT_PSN &&
            cmp_psn(qp->s_sending_psn, qp->s_sending_hpsn) > 0) {
                qp->s_flags &= ~RVT_S_WAIT_PSN;
                qp->s_sending_psn = qp->s_psn;
                qp->s_sending_hpsn = qp->s_psn - 1;
                hfi1_schedule_send(qp);
        }
}

static inline void update_last_psn(struct rvt_qp *qp, u32 psn)
{
        qp->s_last_psn = psn;
}

/*
 * Generate a SWQE completion.
 * This is similar to hfi1_send_complete but has to check to be sure
 * that the SGEs are not being referenced if the SWQE is being resent.
 */
static struct rvt_swqe *do_rc_completion(struct rvt_qp *qp,
                                         struct rvt_swqe *wqe,
                                         struct hfi1_ibport *ibp)
{
        lockdep_assert_held(&qp->s_lock);
        /*
         * Don't decrement refcount and don't generate a
         * completion if the SWQE is being resent until the send
         * is finished.
         */
        if (cmp_psn(wqe->lpsn, qp->s_sending_psn) < 0 ||
            cmp_psn(qp->s_sending_psn, qp->s_sending_hpsn) > 0) {
                u32 s_last;

                rvt_put_swqe(wqe);
                s_last = qp->s_last;
                if (++s_last >= qp->s_size)
                        s_last = 0;
                qp->s_last = s_last;
                /* see post_send() */
                barrier();
                rvt_qp_swqe_complete(qp, wqe, IB_WC_SUCCESS);
        } else {
                struct hfi1_pportdata *ppd = ppd_from_ibp(ibp);

                this_cpu_inc(*ibp->rvp.rc_delayed_comp);
                /*
                 * If send progress not running attempt to progress
                 * SDMA queue.
                 */
                if (ppd->dd->flags & HFI1_HAS_SEND_DMA) {
                        struct sdma_engine *engine;
                        u8 sc5;

                        /* For now use sc to find engine */
                        sc5 = ibp->sl_to_sc[qp->remote_ah_attr.sl];
                        engine = qp_to_sdma_engine(qp, sc5);
                        sdma_engine_progress_schedule(engine);
                }
        }

        qp->s_retry = qp->s_retry_cnt;
        update_last_psn(qp, wqe->lpsn);

        /*
         * If we are completing a request which is in the process of
         * being resent, we can stop re-sending it since we know the
         * responder has already seen it.
         */
        if (qp->s_acked == qp->s_cur) {
                if (++qp->s_cur >= qp->s_size)
                        qp->s_cur = 0;
                qp->s_acked = qp->s_cur;
                wqe = rvt_get_swqe_ptr(qp, qp->s_cur);
                if (qp->s_acked != qp->s_tail) {
                        qp->s_state = OP(SEND_LAST);
                        qp->s_psn = wqe->psn;
                }
        } else {
                if (++qp->s_acked >= qp->s_size)
                        qp->s_acked = 0;
                if (qp->state == IB_QPS_SQD && qp->s_acked == qp->s_cur)
                        qp->s_draining = 0;
                wqe = rvt_get_swqe_ptr(qp, qp->s_acked);
        }
        return wqe;
}

/**
 * do_rc_ack - process an incoming RC ACK
 * @qp: the QP the ACK came in on
 * @psn: the packet sequence number of the ACK
 * @opcode: the opcode of the request that resulted in the ACK
 *
 * This is called from rc_rcv_resp() to process an incoming RC ACK
 * for the given QP.
 * May be called at interrupt level, with the QP s_lock held.
 * Returns 1 if OK, 0 if current operation should be aborted (NAK).
 */
static int do_rc_ack(struct rvt_qp *qp, u32 aeth, u32 psn, int opcode,
                     u64 val, struct hfi1_ctxtdata *rcd)
{
        struct hfi1_ibport *ibp;
        enum ib_wc_status status;
        struct rvt_swqe *wqe;
        int ret = 0;
        u32 ack_psn;
        int diff;
        unsigned long to;

        lockdep_assert_held(&qp->s_lock);
        /*
         * Note that NAKs implicitly ACK outstanding SEND and RDMA write
         * requests and implicitly NAK RDMA read and atomic requests issued
         * before the NAK'ed request.  The MSN won't include the NAK'ed
         * request but will include an ACK'ed request(s).
         */
        ack_psn = psn;
        if (aeth >> 29)
                ack_psn--;
        wqe = rvt_get_swqe_ptr(qp, qp->s_acked);
        ibp = rcd_to_iport(rcd);

        /*
         * The MSN might be for a later WQE than the PSN indicates so
         * only complete WQEs that the PSN finishes.
         */
        while ((diff = delta_psn(ack_psn, wqe->lpsn)) >= 0) {
                /*
                 * RDMA_READ_RESPONSE_ONLY is a special case since
                 * we want to generate completion events for everything
                 * before the RDMA read, copy the data, then generate
                 * the completion for the read.
                 */
                if (wqe->wr.opcode == IB_WR_RDMA_READ &&
                    opcode == OP(RDMA_READ_RESPONSE_ONLY) &&
                    diff == 0) {
                        ret = 1;
                        goto bail_stop;
                }
                /*
                 * If this request is a RDMA read or atomic, and the ACK is
                 * for a later operation, this ACK NAKs the RDMA read or
                 * atomic.  In other words, only a RDMA_READ_LAST or ONLY
                 * can ACK a RDMA read and likewise for atomic ops.  Note
                 * that the NAK case can only happen if relaxed ordering is
                 * used and requests are sent after an RDMA read or atomic
                 * is sent but before the response is received.
                 */
                if ((wqe->wr.opcode == IB_WR_RDMA_READ &&
                     (opcode != OP(RDMA_READ_RESPONSE_LAST) || diff != 0)) ||
                    ((wqe->wr.opcode == IB_WR_ATOMIC_CMP_AND_SWP ||
                      wqe->wr.opcode == IB_WR_ATOMIC_FETCH_AND_ADD) &&
                     (opcode != OP(ATOMIC_ACKNOWLEDGE) || diff != 0))) {
                        /* Retry this request. */
                        if (!(qp->r_flags & RVT_R_RDMAR_SEQ)) {
                                qp->r_flags |= RVT_R_RDMAR_SEQ;
                                restart_rc(qp, qp->s_last_psn + 1, 0);
                                if (list_empty(&qp->rspwait)) {
                                        qp->r_flags |= RVT_R_RSP_SEND;
                                        rvt_get_qp(qp);
                                        list_add_tail(&qp->rspwait,
                                                      &rcd->qp_wait_list);
                                }
                        }
                        /*
                         * No need to process the ACK/NAK since we are
                         * restarting an earlier request.
                         */
                        goto bail_stop;
                }
                if (wqe->wr.opcode == IB_WR_ATOMIC_CMP_AND_SWP ||
                    wqe->wr.opcode == IB_WR_ATOMIC_FETCH_AND_ADD) {
                        u64 *vaddr = wqe->sg_list[0].vaddr;
                        *vaddr = val;
                }
                if (qp->s_num_rd_atomic &&
                    (wqe->wr.opcode == IB_WR_RDMA_READ ||
                     wqe->wr.opcode == IB_WR_ATOMIC_CMP_AND_SWP ||
                     wqe->wr.opcode == IB_WR_ATOMIC_FETCH_AND_ADD)) {
                        qp->s_num_rd_atomic--;
                        /* Restart sending task if fence is complete */
                        if ((qp->s_flags & RVT_S_WAIT_FENCE) &&
                            !qp->s_num_rd_atomic) {
                                qp->s_flags &= ~(RVT_S_WAIT_FENCE |
                                                 RVT_S_WAIT_ACK);
                                hfi1_schedule_send(qp);
                        } else if (qp->s_flags & RVT_S_WAIT_RDMAR) {
                                qp->s_flags &= ~(RVT_S_WAIT_RDMAR |
                                                 RVT_S_WAIT_ACK);
                                hfi1_schedule_send(qp);
                        }
                }
                wqe = do_rc_completion(qp, wqe, ibp);
                if (qp->s_acked == qp->s_tail)
                        break;
        }

        switch (aeth >> 29) {
        case 0:         /* ACK */
                this_cpu_inc(*ibp->rvp.rc_acks);
                if (qp->s_acked != qp->s_tail) {
                        /*
                         * We are expecting more ACKs so
                         * mod the retry timer.
                         */
                        hfi1_mod_retry_timer(qp);
                        /*
                         * We can stop re-sending the earlier packets and
                         * continue with the next packet the receiver wants.
                         */
                        if (cmp_psn(qp->s_psn, psn) <= 0)
                                reset_psn(qp, psn + 1);
                } else {
                        /* No more acks - kill all timers */
                        hfi1_stop_rc_timers(qp);
                        if (cmp_psn(qp->s_psn, psn) <= 0) {
                                qp->s_state = OP(SEND_LAST);
                                qp->s_psn = psn + 1;
                        }
                }
                if (qp->s_flags & RVT_S_WAIT_ACK) {
                        qp->s_flags &= ~RVT_S_WAIT_ACK;
                        hfi1_schedule_send(qp);
                }
                hfi1_get_credit(qp, aeth);
                qp->s_rnr_retry = qp->s_rnr_retry_cnt;
                qp->s_retry = qp->s_retry_cnt;
                update_last_psn(qp, psn);
                return 1;

        case 1:         /* RNR NAK */
                ibp->rvp.n_rnr_naks++;
                if (qp->s_acked == qp->s_tail)
                        goto bail_stop;
                if (qp->s_flags & RVT_S_WAIT_RNR)
                        goto bail_stop;
                if (qp->s_rnr_retry == 0) {
                        status = IB_WC_RNR_RETRY_EXC_ERR;
                        goto class_b;
                }
                if (qp->s_rnr_retry_cnt < 7)
                        qp->s_rnr_retry--;

                /* The last valid PSN is the previous PSN. */
                update_last_psn(qp, psn - 1);

                ibp->rvp.n_rc_resends += delta_psn(qp->s_psn, psn);

                reset_psn(qp, psn);

                qp->s_flags &= ~(RVT_S_WAIT_SSN_CREDIT | RVT_S_WAIT_ACK);
                hfi1_stop_rc_timers(qp);
                to =
                        ib_hfi1_rnr_table[(aeth >> HFI1_AETH_CREDIT_SHIFT) &
                                           HFI1_AETH_CREDIT_MASK];
                hfi1_add_rnr_timer(qp, to);
                return 0;

        case 3:         /* NAK */
                if (qp->s_acked == qp->s_tail)
                        goto bail_stop;
                /* The last valid PSN is the previous PSN. */
                update_last_psn(qp, psn - 1);
                switch ((aeth >> HFI1_AETH_CREDIT_SHIFT) &
                        HFI1_AETH_CREDIT_MASK) {
                case 0: /* PSN sequence error */
                        ibp->rvp.n_seq_naks++;
                        /*
                         * Back up to the responder's expected PSN.
                         * Note that we might get a NAK in the middle of an
                         * RDMA READ response which terminates the RDMA
                         * READ.
                         */
                        restart_rc(qp, psn, 0);
                        hfi1_schedule_send(qp);
                        break;

                case 1: /* Invalid Request */
                        status = IB_WC_REM_INV_REQ_ERR;
                        ibp->rvp.n_other_naks++;
                        goto class_b;

                case 2: /* Remote Access Error */
                        status = IB_WC_REM_ACCESS_ERR;
                        ibp->rvp.n_other_naks++;
                        goto class_b;

                case 3: /* Remote Operation Error */
                        status = IB_WC_REM_OP_ERR;
                        ibp->rvp.n_other_naks++;
class_b:
                        if (qp->s_last == qp->s_acked) {
                                hfi1_send_complete(qp, wqe, status);
                                rvt_error_qp(qp, IB_WC_WR_FLUSH_ERR);
                        }
                        break;

                default:
                        /* Ignore other reserved NAK error codes */
                        goto reserved;
                }
                qp->s_retry = qp->s_retry_cnt;
                qp->s_rnr_retry = qp->s_rnr_retry_cnt;
                goto bail_stop;

        default:                /* 2: reserved */
reserved:
                /* Ignore reserved NAK codes. */
                goto bail_stop;
        }
        /* cannot be reached  */
bail_stop:
        hfi1_stop_rc_timers(qp);
        return ret;
}

/*
 * We have seen an out of sequence RDMA read middle or last packet.
 * This ACKs SENDs and RDMA writes up to the first RDMA read or atomic SWQE.
 */
static void rdma_seq_err(struct rvt_qp *qp, struct hfi1_ibport *ibp, u32 psn,
                         struct hfi1_ctxtdata *rcd)
{
        struct rvt_swqe *wqe;

        lockdep_assert_held(&qp->s_lock);
        /* Remove QP from retry timer */
        hfi1_stop_rc_timers(qp);

        wqe = rvt_get_swqe_ptr(qp, qp->s_acked);

        while (cmp_psn(psn, wqe->lpsn) > 0) {
                if (wqe->wr.opcode == IB_WR_RDMA_READ ||
                    wqe->wr.opcode == IB_WR_ATOMIC_CMP_AND_SWP ||
                    wqe->wr.opcode == IB_WR_ATOMIC_FETCH_AND_ADD)
                        break;
                wqe = do_rc_completion(qp, wqe, ibp);
        }

        ibp->rvp.n_rdma_seq++;
        qp->r_flags |= RVT_R_RDMAR_SEQ;
        restart_rc(qp, qp->s_last_psn + 1, 0);
        if (list_empty(&qp->rspwait)) {
                qp->r_flags |= RVT_R_RSP_SEND;
                rvt_get_qp(qp);
                list_add_tail(&qp->rspwait, &rcd->qp_wait_list);
        }
}

/**
 * rc_rcv_resp - process an incoming RC response packet
 * @ibp: the port this packet came in on
 * @ohdr: the other headers for this packet
 * @data: the packet data
 * @tlen: the packet length
 * @qp: the QP for this packet
 * @opcode: the opcode for this packet
 * @psn: the packet sequence number for this packet
 * @hdrsize: the header length
 * @pmtu: the path MTU
 *
 * This is called from hfi1_rc_rcv() to process an incoming RC response
 * packet for the given QP.
 * Called at interrupt level.
 */
static void rc_rcv_resp(struct hfi1_ibport *ibp,
                        struct ib_other_headers *ohdr,
                        void *data, u32 tlen, struct rvt_qp *qp,
                        u32 opcode, u32 psn, u32 hdrsize, u32 pmtu,
                        struct hfi1_ctxtdata *rcd)
{
        struct rvt_swqe *wqe;
        enum ib_wc_status status;
        unsigned long flags;
        int diff;
        u32 pad;
        u32 aeth;
        u64 val;

        spin_lock_irqsave(&qp->s_lock, flags);

        trace_hfi1_ack(qp, psn);

        /* Ignore invalid responses. */
        smp_read_barrier_depends(); /* see post_one_send */
        if (cmp_psn(psn, READ_ONCE(qp->s_next_psn)) >= 0)
                goto ack_done;

        /* Ignore duplicate responses. */
        diff = cmp_psn(psn, qp->s_last_psn);
        if (unlikely(diff <= 0)) {
                /* Update credits for "ghost" ACKs */
                if (diff == 0 && opcode == OP(ACKNOWLEDGE)) {
                        aeth = be32_to_cpu(ohdr->u.aeth);
                        if ((aeth >> 29) == 0)
                                hfi1_get_credit(qp, aeth);
                }
                goto ack_done;
        }

        /*
         * Skip everything other than the PSN we expect, if we are waiting
         * for a reply to a restarted RDMA read or atomic op.
         */
        if (qp->r_flags & RVT_R_RDMAR_SEQ) {
                if (cmp_psn(psn, qp->s_last_psn + 1) != 0)
                        goto ack_done;
                qp->r_flags &= ~RVT_R_RDMAR_SEQ;
        }

        if (unlikely(qp->s_acked == qp->s_tail))
                goto ack_done;
        wqe = rvt_get_swqe_ptr(qp, qp->s_acked);
        status = IB_WC_SUCCESS;

        switch (opcode) {
        case OP(ACKNOWLEDGE):
        case OP(ATOMIC_ACKNOWLEDGE):
        case OP(RDMA_READ_RESPONSE_FIRST):
                aeth = be32_to_cpu(ohdr->u.aeth);
                if (opcode == OP(ATOMIC_ACKNOWLEDGE))
                        val = ib_u64_get(&ohdr->u.at.atomic_ack_eth);
                else
                        val = 0;
                if (!do_rc_ack(qp, aeth, psn, opcode, val, rcd) ||
                    opcode != OP(RDMA_READ_RESPONSE_FIRST))
                        goto ack_done;
                wqe = rvt_get_swqe_ptr(qp, qp->s_acked);
                if (unlikely(wqe->wr.opcode != IB_WR_RDMA_READ))
                        goto ack_op_err;
                /*
                 * If this is a response to a resent RDMA read, we
                 * have to be careful to copy the data to the right
                 * location.
                 */
                qp->s_rdma_read_len = restart_sge(&qp->s_rdma_read_sge,
                                                  wqe, psn, pmtu);
                goto read_middle;

        case OP(RDMA_READ_RESPONSE_MIDDLE):
                /* no AETH, no ACK */
                if (unlikely(cmp_psn(psn, qp->s_last_psn + 1)))
                        goto ack_seq_err;
                if (unlikely(wqe->wr.opcode != IB_WR_RDMA_READ))
                        goto ack_op_err;
read_middle:
                if (unlikely(tlen != (hdrsize + pmtu + 4)))
                        goto ack_len_err;
                if (unlikely(pmtu >= qp->s_rdma_read_len))
                        goto ack_len_err;

                /*
                 * We got a response so update the timeout.
                 * 4.096 usec. * (1 << qp->timeout)
                 */
                qp->s_flags |= RVT_S_TIMER;
                mod_timer(&qp->s_timer, jiffies + qp->timeout_jiffies);
                if (qp->s_flags & RVT_S_WAIT_ACK) {
                        qp->s_flags &= ~RVT_S_WAIT_ACK;
                        hfi1_schedule_send(qp);
                }

                if (opcode == OP(RDMA_READ_RESPONSE_MIDDLE))
                        qp->s_retry = qp->s_retry_cnt;

                /*
                 * Update the RDMA receive state but do the copy w/o
                 * holding the locks and blocking interrupts.
                 */
                qp->s_rdma_read_len -= pmtu;
                update_last_psn(qp, psn);
                spin_unlock_irqrestore(&qp->s_lock, flags);
                hfi1_copy_sge(&qp->s_rdma_read_sge, data, pmtu, 0, 0);
                goto bail;

        case OP(RDMA_READ_RESPONSE_ONLY):
                aeth = be32_to_cpu(ohdr->u.aeth);
                if (!do_rc_ack(qp, aeth, psn, opcode, 0, rcd))
                        goto ack_done;
                /* Get the number of bytes the message was padded by. */
                pad = (be32_to_cpu(ohdr->bth[0]) >> 20) & 3;
                /*
                 * Check that the data size is >= 0 && <= pmtu.
                 * Remember to account for ICRC (4).
                 */
                if (unlikely(tlen < (hdrsize + pad + 4)))
                        goto ack_len_err;
                /*
                 * If this is a response to a resent RDMA read, we
                 * have to be careful to copy the data to the right
                 * location.
                 */
                wqe = rvt_get_swqe_ptr(qp, qp->s_acked);
                qp->s_rdma_read_len = restart_sge(&qp->s_rdma_read_sge,
                                                  wqe, psn, pmtu);
                goto read_last;

        case OP(RDMA_READ_RESPONSE_LAST):
                /* ACKs READ req. */
                if (unlikely(cmp_psn(psn, qp->s_last_psn + 1)))
                        goto ack_seq_err;
                if (unlikely(wqe->wr.opcode != IB_WR_RDMA_READ))
                        goto ack_op_err;
                /* Get the number of bytes the message was padded by. */
                pad = (be32_to_cpu(ohdr->bth[0]) >> 20) & 3;
                /*
                 * Check that the data size is >= 1 && <= pmtu.
                 * Remember to account for ICRC (4).
                 */
                if (unlikely(tlen <= (hdrsize + pad + 4)))
                        goto ack_len_err;
read_last:
                tlen -= hdrsize + pad + 4;
                if (unlikely(tlen != qp->s_rdma_read_len))
                        goto ack_len_err;
                aeth = be32_to_cpu(ohdr->u.aeth);
                hfi1_copy_sge(&qp->s_rdma_read_sge, data, tlen, 0, 0);
                WARN_ON(qp->s_rdma_read_sge.num_sge);
                (void)do_rc_ack(qp, aeth, psn,
                                 OP(RDMA_READ_RESPONSE_LAST), 0, rcd);
                goto ack_done;
        }

ack_op_err:
        status = IB_WC_LOC_QP_OP_ERR;
        goto ack_err;

ack_seq_err:
        rdma_seq_err(qp, ibp, psn, rcd);
        goto ack_done;

ack_len_err:
        status = IB_WC_LOC_LEN_ERR;
ack_err:
        if (qp->s_last == qp->s_acked) {
                hfi1_send_complete(qp, wqe, status);
                rvt_error_qp(qp, IB_WC_WR_FLUSH_ERR);
        }
ack_done:
        spin_unlock_irqrestore(&qp->s_lock, flags);
bail:
        return;
}

static inline void rc_defered_ack(struct hfi1_ctxtdata *rcd,
                                  struct rvt_qp *qp)
{
        if (list_empty(&qp->rspwait)) {
                qp->r_flags |= RVT_R_RSP_NAK;
                rvt_get_qp(qp);
                list_add_tail(&qp->rspwait, &rcd->qp_wait_list);
        }
}

static inline void rc_cancel_ack(struct rvt_qp *qp)
{
        struct hfi1_qp_priv *priv = qp->priv;

        priv->r_adefered = 0;
        if (list_empty(&qp->rspwait))
                return;
        list_del_init(&qp->rspwait);
        qp->r_flags &= ~RVT_R_RSP_NAK;
        rvt_put_qp(qp);
}

/**
 * rc_rcv_error - process an incoming duplicate or error RC packet
 * @ohdr: the other headers for this packet
 * @data: the packet data
 * @qp: the QP for this packet
 * @opcode: the opcode for this packet
 * @psn: the packet sequence number for this packet
 * @diff: the difference between the PSN and the expected PSN
 *
 * This is called from hfi1_rc_rcv() to process an unexpected
 * incoming RC packet for the given QP.
 * Called at interrupt level.
 * Return 1 if no more processing is needed; otherwise return 0 to
 * schedule a response to be sent.
 */
static noinline int rc_rcv_error(struct ib_other_headers *ohdr, void *data,
                                 struct rvt_qp *qp, u32 opcode, u32 psn,
                                 int diff, struct hfi1_ctxtdata *rcd)
{
        struct hfi1_ibport *ibp = rcd_to_iport(rcd);
        struct rvt_ack_entry *e;
        unsigned long flags;
        u8 i, prev;
        int old_req;

        trace_hfi1_rcv_error(qp, psn);
        if (diff > 0) {
                /*
                 * Packet sequence error.
                 * A NAK will ACK earlier sends and RDMA writes.
                 * Don't queue the NAK if we already sent one.
                 */
                if (!qp->r_nak_state) {
                        ibp->rvp.n_rc_seqnak++;
                        qp->r_nak_state = IB_NAK_PSN_ERROR;
                        /* Use the expected PSN. */
                        qp->r_ack_psn = qp->r_psn;
                        /*
                         * Wait to send the sequence NAK until all packets
                         * in the receive queue have been processed.
                         * Otherwise, we end up propagating congestion.
                         */
                        rc_defered_ack(rcd, qp);
                }
                goto done;
        }

        /*
         * Handle a duplicate request.  Don't re-execute SEND, RDMA
         * write or atomic op.  Don't NAK errors, just silently drop
         * the duplicate request.  Note that r_sge, r_len, and
         * r_rcv_len may be in use so don't modify them.
         *
         * We are supposed to ACK the earliest duplicate PSN but we
         * can coalesce an outstanding duplicate ACK.  We have to
         * send the earliest so that RDMA reads can be restarted at
         * the requester's expected PSN.
         *
         * First, find where this duplicate PSN falls within the
         * ACKs previously sent.
         * old_req is true if there is an older response that is scheduled
         * to be sent before sending this one.
         */
        e = NULL;
        old_req = 1;
        ibp->rvp.n_rc_dupreq++;

        spin_lock_irqsave(&qp->s_lock, flags);

        for (i = qp->r_head_ack_queue; ; i = prev) {
                if (i == qp->s_tail_ack_queue)
                        old_req = 0;
                if (i)
                        prev = i - 1;
                else
                        prev = HFI1_MAX_RDMA_ATOMIC;
                if (prev == qp->r_head_ack_queue) {
                        e = NULL;
                        break;
                }
                e = &qp->s_ack_queue[prev];
                if (!e->opcode) {
                        e = NULL;
                        break;
                }
                if (cmp_psn(psn, e->psn) >= 0) {
                        if (prev == qp->s_tail_ack_queue &&
                            cmp_psn(psn, e->lpsn) <= 0)
                                old_req = 0;
                        break;
                }
        }
        switch (opcode) {
        case OP(RDMA_READ_REQUEST): {
                struct ib_reth *reth;
                u32 offset;
                u32 len;

                /*
                 * If we didn't find the RDMA read request in the ack queue,
                 * we can ignore this request.
                 */
                if (!e || e->opcode != OP(RDMA_READ_REQUEST))
                        goto unlock_done;
                /* RETH comes after BTH */
                reth = &ohdr->u.rc.reth;
                /*
                 * Address range must be a subset of the original
                 * request and start on pmtu boundaries.
                 * We reuse the old ack_queue slot since the requester
                 * should not back up and request an earlier PSN for the
                 * same request.
                 */
                offset = delta_psn(psn, e->psn) * qp->pmtu;
                len = be32_to_cpu(reth->length);
                if (unlikely(offset + len != e->rdma_sge.sge_length))
                        goto unlock_done;
                if (e->rdma_sge.mr) {
                        rvt_put_mr(e->rdma_sge.mr);
                        e->rdma_sge.mr = NULL;
                }
                if (len != 0) {
                        u32 rkey = be32_to_cpu(reth->rkey);
                        u64 vaddr = get_ib_reth_vaddr(reth);
                        int ok;

                        ok = rvt_rkey_ok(qp, &e->rdma_sge, len, vaddr, rkey,
                                         IB_ACCESS_REMOTE_READ);
                        if (unlikely(!ok))
                                goto unlock_done;
                } else {
                        e->rdma_sge.vaddr = NULL;
                        e->rdma_sge.length = 0;
                        e->rdma_sge.sge_length = 0;
                }
                e->psn = psn;
                if (old_req)
                        goto unlock_done;
                qp->s_tail_ack_queue = prev;
                break;
        }

        case OP(COMPARE_SWAP):
        case OP(FETCH_ADD): {
                /*
                 * If we didn't find the atomic request in the ack queue
                 * or the send engine is already backed up to send an
                 * earlier entry, we can ignore this request.
                 */
                if (!e || e->opcode != (u8)opcode || old_req)
                        goto unlock_done;
                qp->s_tail_ack_queue = prev;
                break;
        }

        default:
                /*
                 * Ignore this operation if it doesn't request an ACK
                 * or an earlier RDMA read or atomic is going to be resent.
                 */
                if (!(psn & IB_BTH_REQ_ACK) || old_req)
                        goto unlock_done;
                /*
                 * Resend the most recent ACK if this request is
                 * after all the previous RDMA reads and atomics.
                 */
                if (i == qp->r_head_ack_queue) {
                        spin_unlock_irqrestore(&qp->s_lock, flags);
                        qp->r_nak_state = 0;
                        qp->r_ack_psn = qp->r_psn - 1;
                        goto send_ack;
                }

                /*
                 * Resend the RDMA read or atomic op which
                 * ACKs this duplicate request.
                 */
                qp->s_tail_ack_queue = i;
                break;
        }
        qp->s_ack_state = OP(ACKNOWLEDGE);
        qp->s_flags |= RVT_S_RESP_PENDING;
        qp->r_nak_state = 0;
        hfi1_schedule_send(qp);

unlock_done:
        spin_unlock_irqrestore(&qp->s_lock, flags);
done:
        return 1;

send_ack:
        return 0;
}

static inline void update_ack_queue(struct rvt_qp *qp, unsigned n)
{
        unsigned next;

        next = n + 1;
        if (next > HFI1_MAX_RDMA_ATOMIC)
                next = 0;
        qp->s_tail_ack_queue = next;
        qp->s_ack_state = OP(ACKNOWLEDGE);
}

static void log_cca_event(struct hfi1_pportdata *ppd, u8 sl, u32 rlid,
                          u32 lqpn, u32 rqpn, u8 svc_type)
{
        struct opa_hfi1_cong_log_event_internal *cc_event;
        unsigned long flags;

        if (sl >= OPA_MAX_SLS)
                return;

        spin_lock_irqsave(&ppd->cc_log_lock, flags);

        ppd->threshold_cong_event_map[sl / 8] |= 1 << (sl % 8);
        ppd->threshold_event_counter++;

        cc_event = &ppd->cc_events[ppd->cc_log_idx++];
        if (ppd->cc_log_idx == OPA_CONG_LOG_ELEMS)
                ppd->cc_log_idx = 0;
        cc_event->lqpn = lqpn & RVT_QPN_MASK;
        cc_event->rqpn = rqpn & RVT_QPN_MASK;
        cc_event->sl = sl;
        cc_event->svc_type = svc_type;
        cc_event->rlid = rlid;
        /* keep timestamp in units of 1.024 usec */
        cc_event->timestamp = ktime_to_ns(ktime_get()) / 1024;

        spin_unlock_irqrestore(&ppd->cc_log_lock, flags);
}

void process_becn(struct hfi1_pportdata *ppd, u8 sl, u16 rlid, u32 lqpn,
                  u32 rqpn, u8 svc_type)
{
        struct cca_timer *cca_timer;
        u16 ccti, ccti_incr, ccti_timer, ccti_limit;
        u8 trigger_threshold;
        struct cc_state *cc_state;
        unsigned long flags;

        if (sl >= OPA_MAX_SLS)
                return;

        cc_state = get_cc_state(ppd);

        if (!cc_state)
                return;

        /*
         * 1) increase CCTI (for this SL)
         * 2) select IPG (i.e., call set_link_ipg())
         * 3) start timer
         */
        ccti_limit = cc_state->cct.ccti_limit;
        ccti_incr = cc_state->cong_setting.entries[sl].ccti_increase;
        ccti_timer = cc_state->cong_setting.entries[sl].ccti_timer;
        trigger_threshold =
                cc_state->cong_setting.entries[sl].trigger_threshold;

        spin_lock_irqsave(&ppd->cca_timer_lock, flags);

        cca_timer = &ppd->cca_timer[sl];
        if (cca_timer->ccti < ccti_limit) {
                if (cca_timer->ccti + ccti_incr <= ccti_limit)
                        cca_timer->ccti += ccti_incr;
                else
                        cca_timer->ccti = ccti_limit;
                set_link_ipg(ppd);
        }

        ccti = cca_timer->ccti;

        if (!hrtimer_active(&cca_timer->hrtimer)) {
                /* ccti_timer is in units of 1.024 usec */
                unsigned long nsec = 1024 * ccti_timer;

                hrtimer_start(&cca_timer->hrtimer, ns_to_ktime(nsec),
                              HRTIMER_MODE_REL);
        }

        spin_unlock_irqrestore(&ppd->cca_timer_lock, flags);

        if ((trigger_threshold != 0) && (ccti >= trigger_threshold))
                log_cca_event(ppd, sl, rlid, lqpn, rqpn, svc_type);
}

/**
 * hfi1_rc_rcv - process an incoming RC packet
 * @rcd: the context pointer
 * @hdr: the header of this packet
 * @rcv_flags: flags relevant to rcv processing
 * @data: the packet data
 * @tlen: the packet length
 * @qp: the QP for this packet
 *
 * This is called from qp_rcv() to process an incoming RC packet
 * for the given QP.
 * May be called at interrupt level.
 */
void hfi1_rc_rcv(struct hfi1_packet *packet)
{
        struct hfi1_ctxtdata *rcd = packet->rcd;
        struct ib_header *hdr = packet->hdr;
        u32 rcv_flags = packet->rcv_flags;
        void *data = packet->ebuf;
        u32 tlen = packet->tlen;
        struct rvt_qp *qp = packet->qp;
        struct hfi1_ibport *ibp = rcd_to_iport(rcd);
        struct ib_other_headers *ohdr = packet->ohdr;
        u32 bth0, opcode;
        u32 hdrsize = packet->hlen;
        u32 psn;
        u32 pad;
        struct ib_wc wc;
        u32 pmtu = qp->pmtu;
        int diff;
        struct ib_reth *reth;
        unsigned long flags;
        int ret, is_fecn = 0;
        int copy_last = 0;
        u32 rkey;

        lockdep_assert_held(&qp->r_lock);
        bth0 = be32_to_cpu(ohdr->bth[0]);
        if (hfi1_ruc_check_hdr(ibp, hdr, rcv_flags & HFI1_HAS_GRH, qp, bth0))
                return;

        is_fecn = process_ecn(qp, packet, false);

        psn = be32_to_cpu(ohdr->bth[2]);
        opcode = (bth0 >> 24) & 0xff;

        /*
         * Process responses (ACKs) before anything else.  Note that the
         * packet sequence number will be for something in the send work
         * queue rather than the expected receive packet sequence number.
         * In other words, this QP is the requester.
         */
        if (opcode >= OP(RDMA_READ_RESPONSE_FIRST) &&
            opcode <= OP(ATOMIC_ACKNOWLEDGE)) {
                rc_rcv_resp(ibp, ohdr, data, tlen, qp, opcode, psn,
                            hdrsize, pmtu, rcd);
                if (is_fecn)
                        goto send_ack;
                return;
        }

        /* Compute 24 bits worth of difference. */
        diff = delta_psn(psn, qp->r_psn);
        if (unlikely(diff)) {
                if (rc_rcv_error(ohdr, data, qp, opcode, psn, diff, rcd))
                        return;
                goto send_ack;
        }

        /* Check for opcode sequence errors. */
        switch (qp->r_state) {
        case OP(SEND_FIRST):
        case OP(SEND_MIDDLE):
                if (opcode == OP(SEND_MIDDLE) ||
                    opcode == OP(SEND_LAST) ||
                    opcode == OP(SEND_LAST_WITH_IMMEDIATE) ||
                    opcode == OP(SEND_LAST_WITH_INVALIDATE))
                        break;
                goto nack_inv;

        case OP(RDMA_WRITE_FIRST):
        case OP(RDMA_WRITE_MIDDLE):
                if (opcode == OP(RDMA_WRITE_MIDDLE) ||
                    opcode == OP(RDMA_WRITE_LAST) ||
                    opcode == OP(RDMA_WRITE_LAST_WITH_IMMEDIATE))
                        break;
                goto nack_inv;

        default:
                if (opcode == OP(SEND_MIDDLE) ||
                    opcode == OP(SEND_LAST) ||
                    opcode == OP(SEND_LAST_WITH_IMMEDIATE) ||
                    opcode == OP(SEND_LAST_WITH_INVALIDATE) ||
                    opcode == OP(RDMA_WRITE_MIDDLE) ||
                    opcode == OP(RDMA_WRITE_LAST) ||
                    opcode == OP(RDMA_WRITE_LAST_WITH_IMMEDIATE))
                        goto nack_inv;
                /*
                 * Note that it is up to the requester to not send a new
                 * RDMA read or atomic operation before receiving an ACK
                 * for the previous operation.
                 */
                break;
        }

        if (qp->state == IB_QPS_RTR && !(qp->r_flags & RVT_R_COMM_EST))
                rvt_comm_est(qp);

        /* OK, process the packet. */
        switch (opcode) {
        case OP(SEND_FIRST):
                ret = hfi1_rvt_get_rwqe(qp, 0);
                if (ret < 0)
                        goto nack_op_err;
                if (!ret)
                        goto rnr_nak;
                qp->r_rcv_len = 0;
                /* FALLTHROUGH */
        case OP(SEND_MIDDLE):
        case OP(RDMA_WRITE_MIDDLE):
send_middle:
                /* Check for invalid length PMTU or posted rwqe len. */
                if (unlikely(tlen != (hdrsize + pmtu + 4)))
                        goto nack_inv;
                qp->r_rcv_len += pmtu;
                if (unlikely(qp->r_rcv_len > qp->r_len))
                        goto nack_inv;
                hfi1_copy_sge(&qp->r_sge, data, pmtu, 1, 0);
                break;

        case OP(RDMA_WRITE_LAST_WITH_IMMEDIATE):
                /* consume RWQE */
                ret = hfi1_rvt_get_rwqe(qp, 1);
                if (ret < 0)
                        goto nack_op_err;
                if (!ret)
                        goto rnr_nak;
                goto send_last_imm;

        case OP(SEND_ONLY):
        case OP(SEND_ONLY_WITH_IMMEDIATE):
        case OP(SEND_ONLY_WITH_INVALIDATE):
                ret = hfi1_rvt_get_rwqe(qp, 0);
                if (ret < 0)
                        goto nack_op_err;
                if (!ret)
                        goto rnr_nak;
                qp->r_rcv_len = 0;
                if (opcode == OP(SEND_ONLY))
                        goto no_immediate_data;
                if (opcode == OP(SEND_ONLY_WITH_INVALIDATE))
                        goto send_last_inv;
                /* FALLTHROUGH for SEND_ONLY_WITH_IMMEDIATE */
        case OP(SEND_LAST_WITH_IMMEDIATE):
send_last_imm:
                wc.ex.imm_data = ohdr->u.imm_data;
                wc.wc_flags = IB_WC_WITH_IMM;
                goto send_last;
        case OP(SEND_LAST_WITH_INVALIDATE):
send_last_inv:
                rkey = be32_to_cpu(ohdr->u.ieth);
                if (rvt_invalidate_rkey(qp, rkey))
                        goto no_immediate_data;
                wc.ex.invalidate_rkey = rkey;
                wc.wc_flags = IB_WC_WITH_INVALIDATE;
                goto send_last;
        case OP(RDMA_WRITE_LAST):
                copy_last = ibpd_to_rvtpd(qp->ibqp.pd)->user;
                /* fall through */
        case OP(SEND_LAST):
no_immediate_data:
                wc.wc_flags = 0;
                wc.ex.imm_data = 0;
send_last:
                /* Get the number of bytes the message was padded by. */
                pad = (bth0 >> 20) & 3;
                /* Check for invalid length. */
                /* LAST len should be >= 1 */
                if (unlikely(tlen < (hdrsize + pad + 4)))
                        goto nack_inv;
                /* Don't count the CRC. */
                tlen -= (hdrsize + pad + 4);
                wc.byte_len = tlen + qp->r_rcv_len;
                if (unlikely(wc.byte_len > qp->r_len))
                        goto nack_inv;
                hfi1_copy_sge(&qp->r_sge, data, tlen, 1, copy_last);
                rvt_put_ss(&qp->r_sge);
                qp->r_msn++;
                if (!__test_and_clear_bit(RVT_R_WRID_VALID, &qp->r_aflags))
                        break;
                wc.wr_id = qp->r_wr_id;
                wc.status = IB_WC_SUCCESS;
                if (opcode == OP(RDMA_WRITE_LAST_WITH_IMMEDIATE) ||
                    opcode == OP(RDMA_WRITE_ONLY_WITH_IMMEDIATE))
                        wc.opcode = IB_WC_RECV_RDMA_WITH_IMM;
                else
                        wc.opcode = IB_WC_RECV;
                wc.qp = &qp->ibqp;
                wc.src_qp = qp->remote_qpn;
                wc.slid = qp->remote_ah_attr.dlid;
                /*
                 * It seems that IB mandates the presence of an SL in a
                 * work completion only for the UD transport (see section
                 * 11.4.2 of IBTA Vol. 1).
                 *
                 * However, the way the SL is chosen below is consistent
                 * with the way that IB/qib works and is trying avoid
                 * introducing incompatibilities.
                 *
                 * See also OPA Vol. 1, section 9.7.6, and table 9-17.
                 */
                wc.sl = qp->remote_ah_attr.sl;
                /* zero fields that are N/A */
                wc.vendor_err = 0;
                wc.pkey_index = 0;
                wc.dlid_path_bits = 0;
                wc.port_num = 0;
                /* Signal completion event if the solicited bit is set. */
                rvt_cq_enter(ibcq_to_rvtcq(qp->ibqp.recv_cq), &wc,
                             (bth0 & IB_BTH_SOLICITED) != 0);
                break;

        case OP(RDMA_WRITE_ONLY):
                copy_last = 1;
                /* fall through */
        case OP(RDMA_WRITE_FIRST):
        case OP(RDMA_WRITE_ONLY_WITH_IMMEDIATE):
                if (unlikely(!(qp->qp_access_flags & IB_ACCESS_REMOTE_WRITE)))
                        goto nack_inv;
                /* consume RWQE */
                reth = &ohdr->u.rc.reth;
                qp->r_len = be32_to_cpu(reth->length);
                qp->r_rcv_len = 0;
                qp->r_sge.sg_list = NULL;
                if (qp->r_len != 0) {
                        u32 rkey = be32_to_cpu(reth->rkey);
                        u64 vaddr = get_ib_reth_vaddr(reth);
                        int ok;

                        /* Check rkey & NAK */
                        ok = rvt_rkey_ok(qp, &qp->r_sge.sge, qp->r_len, vaddr,
                                         rkey, IB_ACCESS_REMOTE_WRITE);
                        if (unlikely(!ok))
                                goto nack_acc;
                        qp->r_sge.num_sge = 1;
                } else {
                        qp->r_sge.num_sge = 0;
                        qp->r_sge.sge.mr = NULL;
                        qp->r_sge.sge.vaddr = NULL;
                        qp->r_sge.sge.length = 0;
                        qp->r_sge.sge.sge_length = 0;
                }
                if (opcode == OP(RDMA_WRITE_FIRST))
                        goto send_middle;
                else if (opcode == OP(RDMA_WRITE_ONLY))
                        goto no_immediate_data;
                ret = hfi1_rvt_get_rwqe(qp, 1);
                if (ret < 0)
                        goto nack_op_err;
                if (!ret)
                        goto rnr_nak;
                wc.ex.imm_data = ohdr->u.rc.imm_data;
                wc.wc_flags = IB_WC_WITH_IMM;
                goto send_last;

        case OP(RDMA_READ_REQUEST): {
                struct rvt_ack_entry *e;
                u32 len;
                u8 next;

                if (unlikely(!(qp->qp_access_flags & IB_ACCESS_REMOTE_READ)))
                        goto nack_inv;
                next = qp->r_head_ack_queue + 1;
                /* s_ack_queue is size HFI1_MAX_RDMA_ATOMIC+1 so use > not >= */
                if (next > HFI1_MAX_RDMA_ATOMIC)
                        next = 0;
                spin_lock_irqsave(&qp->s_lock, flags);
                if (unlikely(next == qp->s_tail_ack_queue)) {
                        if (!qp->s_ack_queue[next].sent)
                                goto nack_inv_unlck;
                        update_ack_queue(qp, next);
                }
                e = &qp->s_ack_queue[qp->r_head_ack_queue];
                if (e->opcode == OP(RDMA_READ_REQUEST) && e->rdma_sge.mr) {
                        rvt_put_mr(e->rdma_sge.mr);
                        e->rdma_sge.mr = NULL;
                }
                reth = &ohdr->u.rc.reth;
                len = be32_to_cpu(reth->length);
                if (len) {
                        u32 rkey = be32_to_cpu(reth->rkey);
                        u64 vaddr = get_ib_reth_vaddr(reth);
                        int ok;

                        /* Check rkey & NAK */
                        ok = rvt_rkey_ok(qp, &e->rdma_sge, len, vaddr,
                                         rkey, IB_ACCESS_REMOTE_READ);
                        if (unlikely(!ok))
                                goto nack_acc_unlck;
                        /*
                         * Update the next expected PSN.  We add 1 later
                         * below, so only add the remainder here.
                         */
                        qp->r_psn += rvt_div_mtu(qp, len - 1);
                } else {
                        e->rdma_sge.mr = NULL;
                        e->rdma_sge.vaddr = NULL;
                        e->rdma_sge.length = 0;
                        e->rdma_sge.sge_length = 0;
                }
                e->opcode = opcode;
                e->sent = 0;
                e->psn = psn;
                e->lpsn = qp->r_psn;
                /*
                 * We need to increment the MSN here instead of when we
                 * finish sending the result since a duplicate request would
                 * increment it more than once.
                 */
                qp->r_msn++;
                qp->r_psn++;
                qp->r_state = opcode;
                qp->r_nak_state = 0;
                qp->r_head_ack_queue = next;

                /* Schedule the send engine. */
                qp->s_flags |= RVT_S_RESP_PENDING;
                hfi1_schedule_send(qp);

                spin_unlock_irqrestore(&qp->s_lock, flags);
                if (is_fecn)
                        goto send_ack;
                return;
        }

        case OP(COMPARE_SWAP):
        case OP(FETCH_ADD): {
                struct ib_atomic_eth *ateth;
                struct rvt_ack_entry *e;
                u64 vaddr;
                atomic64_t *maddr;
                u64 sdata;
                u32 rkey;
                u8 next;

                if (unlikely(!(qp->qp_access_flags & IB_ACCESS_REMOTE_ATOMIC)))
                        goto nack_inv;
                next = qp->r_head_ack_queue + 1;
                if (next > HFI1_MAX_RDMA_ATOMIC)
                        next = 0;
                spin_lock_irqsave(&qp->s_lock, flags);
                if (unlikely(next == qp->s_tail_ack_queue)) {
                        if (!qp->s_ack_queue[next].sent)
                                goto nack_inv_unlck;
                        update_ack_queue(qp, next);
                }
                e = &qp->s_ack_queue[qp->r_head_ack_queue];
                if (e->opcode == OP(RDMA_READ_REQUEST) && e->rdma_sge.mr) {
                        rvt_put_mr(e->rdma_sge.mr);
                        e->rdma_sge.mr = NULL;
                }
                ateth = &ohdr->u.atomic_eth;
                vaddr = get_ib_ateth_vaddr(ateth);
                if (unlikely(vaddr & (sizeof(u64) - 1)))
                        goto nack_inv_unlck;
                rkey = be32_to_cpu(ateth->rkey);
                /* Check rkey & NAK */
                if (unlikely(!rvt_rkey_ok(qp, &qp->r_sge.sge, sizeof(u64),
                                          vaddr, rkey,
                                          IB_ACCESS_REMOTE_ATOMIC)))
                        goto nack_acc_unlck;
                /* Perform atomic OP and save result. */
                maddr = (atomic64_t *)qp->r_sge.sge.vaddr;
                sdata = get_ib_ateth_swap(ateth);
                e->atomic_data = (opcode == OP(FETCH_ADD)) ?
                        (u64)atomic64_add_return(sdata, maddr) - sdata :
                        (u64)cmpxchg((u64 *)qp->r_sge.sge.vaddr,
                                      get_ib_ateth_compare(ateth),
                                      sdata);
                rvt_put_mr(qp->r_sge.sge.mr);
                qp->r_sge.num_sge = 0;
                e->opcode = opcode;
                e->sent = 0;
                e->psn = psn;
                e->lpsn = psn;
                qp->r_msn++;
                qp->r_psn++;
                qp->r_state = opcode;
                qp->r_nak_state = 0;
                qp->r_head_ack_queue = next;

                /* Schedule the send engine. */
                qp->s_flags |= RVT_S_RESP_PENDING;
                hfi1_schedule_send(qp);

                spin_unlock_irqrestore(&qp->s_lock, flags);
                if (is_fecn)
                        goto send_ack;
                return;
        }

        default:
                /* NAK unknown opcodes. */
                goto nack_inv;
        }
        qp->r_psn++;
        qp->r_state = opcode;
        qp->r_ack_psn = psn;
        qp->r_nak_state = 0;
        /* Send an ACK if requested or required. */
        if (psn & IB_BTH_REQ_ACK) {
                struct hfi1_qp_priv *priv = qp->priv;

                if (packet->numpkt == 0) {
                        rc_cancel_ack(qp);
                        goto send_ack;
                }
                if (priv->r_adefered >= HFI1_PSN_CREDIT) {
                        rc_cancel_ack(qp);
                        goto send_ack;
                }
                if (unlikely(is_fecn)) {
                        rc_cancel_ack(qp);
                        goto send_ack;
                }
                priv->r_adefered++;
                rc_defered_ack(rcd, qp);
        }
        return;

rnr_nak:
        qp->r_nak_state = qp->r_min_rnr_timer | IB_RNR_NAK;
        qp->r_ack_psn = qp->r_psn;
        /* Queue RNR NAK for later */
        rc_defered_ack(rcd, qp);
        return;

nack_op_err:
        rvt_rc_error(qp, IB_WC_LOC_QP_OP_ERR);
        qp->r_nak_state = IB_NAK_REMOTE_OPERATIONAL_ERROR;
        qp->r_ack_psn = qp->r_psn;
        /* Queue NAK for later */
        rc_defered_ack(rcd, qp);
        return;

nack_inv_unlck:
        spin_unlock_irqrestore(&qp->s_lock, flags);
nack_inv:
        rvt_rc_error(qp, IB_WC_LOC_QP_OP_ERR);
        qp->r_nak_state = IB_NAK_INVALID_REQUEST;
        qp->r_ack_psn = qp->r_psn;
        /* Queue NAK for later */
        rc_defered_ack(rcd, qp);
        return;

nack_acc_unlck:
        spin_unlock_irqrestore(&qp->s_lock, flags);
nack_acc:
        rvt_rc_error(qp, IB_WC_LOC_PROT_ERR);
        qp->r_nak_state = IB_NAK_REMOTE_ACCESS_ERROR;
        qp->r_ack_psn = qp->r_psn;
send_ack:
        hfi1_send_rc_ack(rcd, qp, is_fecn);
}

void hfi1_rc_hdrerr(
        struct hfi1_ctxtdata *rcd,
        struct ib_header *hdr,
        u32 rcv_flags,
        struct rvt_qp *qp)
{
        int has_grh = rcv_flags & HFI1_HAS_GRH;
        struct ib_other_headers *ohdr;
        struct hfi1_ibport *ibp = rcd_to_iport(rcd);
        int diff;
        u32 opcode;
        u32 psn, bth0;

        /* Check for GRH */
        ohdr = &hdr->u.oth;
        if (has_grh)
                ohdr = &hdr->u.l.oth;

        bth0 = be32_to_cpu(ohdr->bth[0]);
        if (hfi1_ruc_check_hdr(ibp, hdr, has_grh, qp, bth0))
                return;

        psn = be32_to_cpu(ohdr->bth[2]);
        opcode = (bth0 >> 24) & 0xff;

        /* Only deal with RDMA Writes for now */
        if (opcode < IB_OPCODE_RC_RDMA_READ_RESPONSE_FIRST) {
                diff = delta_psn(psn, qp->r_psn);
                if (!qp->r_nak_state && diff >= 0) {
                        ibp->rvp.n_rc_seqnak++;
                        qp->r_nak_state = IB_NAK_PSN_ERROR;
                        /* Use the expected PSN. */
                        qp->r_ack_psn = qp->r_psn;
                        /*
                         * Wait to send the sequence
                         * NAK until all packets
                         * in the receive queue have
                         * been processed.
                         * Otherwise, we end up
                         * propagating congestion.
                         */
                        rc_defered_ack(rcd, qp);
                } /* Out of sequence NAK */
        } /* QP Request NAKs */
}