2 * SPDX-License-Identifier: MIT
4 * Copyright © 2019 Intel Corporation
10 #include "i915_gem.h" /* GEM_BUG_ON */
11 #include "i915_request.h"
12 #include "intel_ring_types.h"
14 struct intel_engine_cs;
17 intel_engine_create_ring(struct intel_engine_cs *engine, int size);
19 u32 *intel_ring_begin(struct i915_request *rq, unsigned int num_dwords);
20 int intel_ring_cacheline_align(struct i915_request *rq);
22 unsigned int intel_ring_update_space(struct intel_ring *ring);
24 int intel_ring_pin(struct intel_ring *ring);
25 void intel_ring_unpin(struct intel_ring *ring);
26 void intel_ring_reset(struct intel_ring *ring, u32 tail);
28 void intel_ring_free(struct kref *ref);
30 static inline struct intel_ring *intel_ring_get(struct intel_ring *ring)
36 static inline void intel_ring_put(struct intel_ring *ring)
38 kref_put(&ring->ref, intel_ring_free);
41 static inline void intel_ring_advance(struct i915_request *rq, u32 *cs)
45 * This serves as a placeholder in the code so that the reader
46 * can compare against the preceding intel_ring_begin() and
47 * check that the number of dwords emitted matches the space
48 * reserved for the command packet (i.e. the value passed to
49 * intel_ring_begin()).
51 GEM_BUG_ON((rq->ring->vaddr + rq->ring->emit) != cs);
54 static inline u32 intel_ring_wrap(const struct intel_ring *ring, u32 pos)
56 return pos & (ring->size - 1);
59 static inline int intel_ring_direction(const struct intel_ring *ring,
62 typecheck(typeof(ring->size), next);
63 typecheck(typeof(ring->size), prev);
64 return (next - prev) << ring->wrap;
68 intel_ring_offset_valid(const struct intel_ring *ring,
71 if (pos & -ring->size) /* must be strictly within the ring */
74 if (!IS_ALIGNED(pos, 8)) /* must be qword aligned */
80 static inline u32 intel_ring_offset(const struct i915_request *rq, void *addr)
82 /* Don't write ring->size (equivalent to 0) as that hangs some GPUs. */
83 u32 offset = addr - rq->ring->vaddr;
84 GEM_BUG_ON(offset > rq->ring->size);
85 return intel_ring_wrap(rq->ring, offset);
89 assert_ring_tail_valid(const struct intel_ring *ring, unsigned int tail)
91 GEM_BUG_ON(!intel_ring_offset_valid(ring, tail));
95 * Gen2 BSpec "1. Programming Environment" / 1.4.4.6
96 * Gen3 BSpec "1c Memory Interface Functions" / 2.3.4.5
97 * Gen4+ BSpec "1c Memory Interface and Command Stream" / 5.3.4.5
98 * "If the Ring Buffer Head Pointer and the Tail Pointer are on the
99 * same cacheline, the Head Pointer must not be greater than the Tail
102 * We use ring->head as the last known location of the actual RING_HEAD,
103 * it may have advanced but in the worst case it is equally the same
104 * as ring->head and so we should never program RING_TAIL to advance
105 * into the same cacheline as ring->head.
107 #define cacheline(a) round_down(a, CACHELINE_BYTES)
108 GEM_BUG_ON(cacheline(tail) == cacheline(ring->head) &&
113 static inline unsigned int
114 intel_ring_set_tail(struct intel_ring *ring, unsigned int tail)
116 /* Whilst writes to the tail are strictly order, there is no
117 * serialisation between readers and the writers. The tail may be
118 * read by i915_request_retire() just as it is being updated
119 * by execlists, as although the breadcrumb is complete, the context
120 * switch hasn't been seen.
122 assert_ring_tail_valid(ring, tail);
127 static inline unsigned int
128 __intel_ring_space(unsigned int head, unsigned int tail, unsigned int size)
131 * "If the Ring Buffer Head Pointer and the Tail Pointer are on the
132 * same cacheline, the Head Pointer must not be greater than the Tail
135 GEM_BUG_ON(!is_power_of_2(size));
136 return (head - tail - CACHELINE_BYTES) & (size - 1);
139 #endif /* INTEL_RING_H */