+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Intel Speed Select Interface: Mbox via PCI Interface
+ * Copyright (c) 2019, Intel Corporation.
+ * All rights reserved.
+ *
+ * Author: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
+ */
+
+#include <linux/cpufeature.h>
+#include <linux/module.h>
+#include <linux/pci.h>
+#include <linux/sched/signal.h>
+#include <linux/uaccess.h>
+#include <uapi/linux/isst_if.h>
+
+#include "isst_if_common.h"
+
+#define PUNIT_MAILBOX_DATA 0xA0
+#define PUNIT_MAILBOX_INTERFACE 0xA4
+#define PUNIT_MAILBOX_BUSY_BIT 31
+
+/*
+ * Commands has variable amount of processing time. Most of the commands will
+ * be done in 0-3 tries, but some takes up to 50.
+ * The real processing time was observed as 25us for the most of the commands
+ * at 2GHz. It is possible to optimize this count taking samples on customer
+ * systems.
+ */
+#define OS_MAILBOX_RETRY_COUNT 50
+
+struct isst_if_device {
+ struct mutex mutex;
+};
+
+static int isst_if_mbox_cmd(struct pci_dev *pdev,
+ struct isst_if_mbox_cmd *mbox_cmd)
+{
+ u32 retries, data;
+ int ret;
+
+ /* Poll for rb bit == 0 */
+ retries = OS_MAILBOX_RETRY_COUNT;
+ do {
+ ret = pci_read_config_dword(pdev, PUNIT_MAILBOX_INTERFACE,
+ &data);
+ if (ret)
+ return ret;
+
+ if (data & BIT_ULL(PUNIT_MAILBOX_BUSY_BIT)) {
+ ret = -EBUSY;
+ continue;
+ }
+ ret = 0;
+ break;
+ } while (--retries);
+
+ if (ret)
+ return ret;
+
+ /* Write DATA register */
+ ret = pci_write_config_dword(pdev, PUNIT_MAILBOX_DATA,
+ mbox_cmd->req_data);
+ if (ret)
+ return ret;
+
+ /* Write command register */
+ data = BIT_ULL(PUNIT_MAILBOX_BUSY_BIT) |
+ (mbox_cmd->parameter & GENMASK_ULL(13, 0)) << 16 |
+ (mbox_cmd->sub_command << 8) |
+ mbox_cmd->command;
+
+ ret = pci_write_config_dword(pdev, PUNIT_MAILBOX_INTERFACE, data);
+ if (ret)
+ return ret;
+
+ /* Poll for rb bit == 0 */
+ retries = OS_MAILBOX_RETRY_COUNT;
+ do {
+ ret = pci_read_config_dword(pdev, PUNIT_MAILBOX_INTERFACE,
+ &data);
+ if (ret)
+ return ret;
+
+ if (data & BIT_ULL(PUNIT_MAILBOX_BUSY_BIT)) {
+ ret = -EBUSY;
+ continue;
+ }
+
+ if (data & 0xff)
+ return -ENXIO;
+
+ ret = pci_read_config_dword(pdev, PUNIT_MAILBOX_DATA, &data);
+ if (ret)
+ return ret;
+
+ mbox_cmd->resp_data = data;
+ ret = 0;
+ break;
+ } while (--retries);
+
+ return ret;
+}
+
+static long isst_if_mbox_proc_cmd(u8 *cmd_ptr, int *write_only, int resume)
+{
+ struct isst_if_mbox_cmd *mbox_cmd;
+ struct isst_if_device *punit_dev;
+ struct pci_dev *pdev;
+ int ret;
+
+ mbox_cmd = (struct isst_if_mbox_cmd *)cmd_ptr;
+
+ if (isst_if_mbox_cmd_invalid(mbox_cmd))
+ return -EINVAL;
+
+ if (isst_if_mbox_cmd_set_req(mbox_cmd) && !capable(CAP_SYS_ADMIN))
+ return -EPERM;
+
+ pdev = isst_if_get_pci_dev(mbox_cmd->logical_cpu, 1, 30, 1);
+ if (!pdev)
+ return -EINVAL;
+
+ punit_dev = pci_get_drvdata(pdev);
+ if (!punit_dev)
+ return -EINVAL;
+
+ /*
+ * Basically we are allowing one complete mailbox transaction on
+ * a mapped PCI device at a time.
+ */
+ mutex_lock(&punit_dev->mutex);
+ ret = isst_if_mbox_cmd(pdev, mbox_cmd);
+ mutex_unlock(&punit_dev->mutex);
+ if (ret)
+ return ret;
+
+ *write_only = 0;
+
+ return 0;
+}
+
+static const struct pci_device_id isst_if_mbox_ids[] = {
+ { PCI_DEVICE(PCI_VENDOR_ID_INTEL, INTEL_CFG_MBOX_DEVID_0)},
+ { 0 },
+};
+MODULE_DEVICE_TABLE(pci, isst_if_mbox_ids);
+
+static int isst_if_mbox_probe(struct pci_dev *pdev,
+ const struct pci_device_id *ent)
+{
+ struct isst_if_device *punit_dev;
+ struct isst_if_cmd_cb cb;
+ int ret;
+
+ punit_dev = devm_kzalloc(&pdev->dev, sizeof(*punit_dev), GFP_KERNEL);
+ if (!punit_dev)
+ return -ENOMEM;
+
+ ret = pcim_enable_device(pdev);
+ if (ret)
+ return ret;
+
+ mutex_init(&punit_dev->mutex);
+ pci_set_drvdata(pdev, punit_dev);
+
+ memset(&cb, 0, sizeof(cb));
+ cb.cmd_size = sizeof(struct isst_if_mbox_cmd);
+ cb.offset = offsetof(struct isst_if_mbox_cmds, mbox_cmd);
+ cb.cmd_callback = isst_if_mbox_proc_cmd;
+ cb.owner = THIS_MODULE;
+ ret = isst_if_cdev_register(ISST_IF_DEV_MBOX, &cb);
+
+ if (ret)
+ mutex_destroy(&punit_dev->mutex);
+
+ return ret;
+}
+
+static void isst_if_mbox_remove(struct pci_dev *pdev)
+{
+ struct isst_if_device *punit_dev;
+
+ punit_dev = pci_get_drvdata(pdev);
+ isst_if_cdev_unregister(ISST_IF_DEV_MBOX);
+ mutex_destroy(&punit_dev->mutex);
+}
+
+static struct pci_driver isst_if_pci_driver = {
+ .name = "isst_if_mbox_pci",
+ .id_table = isst_if_mbox_ids,
+ .probe = isst_if_mbox_probe,
+ .remove = isst_if_mbox_remove,
+};
+
+module_pci_driver(isst_if_pci_driver);
+
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("Intel speed select interface pci mailbox driver");
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