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/*
* SPDX-License-Identifier: MIT
*
* Copyright © 2019 Intel Corporation
*/
#ifndef INTEL_RING_H
#define INTEL_RING_H
#include "i915_gem.h" /* GEM_BUG_ON */
#include "i915_request.h"
#include "intel_ring_types.h"
struct intel_engine_cs;
struct intel_ring *
intel_engine_create_ring(struct intel_engine_cs *engine, int size);
u32 *intel_ring_begin(struct i915_request *rq, unsigned int num_dwords);
int intel_ring_cacheline_align(struct i915_request *rq);
unsigned int intel_ring_update_space(struct intel_ring *ring);
int intel_ring_pin(struct intel_ring *ring);
void intel_ring_unpin(struct intel_ring *ring);
void intel_ring_reset(struct intel_ring *ring, u32 tail);
void intel_ring_free(struct kref *ref);
static inline struct intel_ring *intel_ring_get(struct intel_ring *ring)
{
kref_get(&ring->ref);
return ring;
}
static inline void intel_ring_put(struct intel_ring *ring)
{
kref_put(&ring->ref, intel_ring_free);
}
static inline void intel_ring_advance(struct i915_request *rq, u32 *cs)
{
/* Dummy function.
*
* This serves as a placeholder in the code so that the reader
* can compare against the preceding intel_ring_begin() and
* check that the number of dwords emitted matches the space
* reserved for the command packet (i.e. the value passed to
* intel_ring_begin()).
*/
GEM_BUG_ON((rq->ring->vaddr + rq->ring->emit) != cs);
}
static inline u32 intel_ring_wrap(const struct intel_ring *ring, u32 pos)
{
return pos & (ring->size - 1);
}
static inline bool
intel_ring_offset_valid(const struct intel_ring *ring,
unsigned int pos)
{
if (pos & -ring->size) /* must be strictly within the ring */
return false;
if (!IS_ALIGNED(pos, 8)) /* must be qword aligned */
return false;
return true;
}
static inline u32 intel_ring_offset(const struct i915_request *rq, void *addr)
{
/* Don't write ring->size (equivalent to 0) as that hangs some GPUs. */
u32 offset = addr - rq->ring->vaddr;
GEM_BUG_ON(offset > rq->ring->size);
return intel_ring_wrap(rq->ring, offset);
}
static inline void
assert_ring_tail_valid(const struct intel_ring *ring, unsigned int tail)
{
GEM_BUG_ON(!intel_ring_offset_valid(ring, tail));
/*
* "Ring Buffer Use"
* Gen2 BSpec "1. Programming Environment" / 1.4.4.6
* Gen3 BSpec "1c Memory Interface Functions" / 2.3.4.5
* Gen4+ BSpec "1c Memory Interface and Command Stream" / 5.3.4.5
* "If the Ring Buffer Head Pointer and the Tail Pointer are on the
* same cacheline, the Head Pointer must not be greater than the Tail
* Pointer."
*
* We use ring->head as the last known location of the actual RING_HEAD,
* it may have advanced but in the worst case it is equally the same
* as ring->head and so we should never program RING_TAIL to advance
* into the same cacheline as ring->head.
*/
#define cacheline(a) round_down(a, CACHELINE_BYTES)
GEM_BUG_ON(cacheline(tail) == cacheline(ring->head) &&
tail < ring->head);
#undef cacheline
}
static inline unsigned int
intel_ring_set_tail(struct intel_ring *ring, unsigned int tail)
{
/* Whilst writes to the tail are strictly order, there is no
* serialisation between readers and the writers. The tail may be
* read by i915_request_retire() just as it is being updated
* by execlists, as although the breadcrumb is complete, the context
* switch hasn't been seen.
*/
assert_ring_tail_valid(ring, tail);
ring->tail = tail;
return tail;
}
static inline unsigned int
__intel_ring_space(unsigned int head, unsigned int tail, unsigned int size)
{
/*
* "If the Ring Buffer Head Pointer and the Tail Pointer are on the
* same cacheline, the Head Pointer must not be greater than the Tail
* Pointer."
*/
GEM_BUG_ON(!is_power_of_2(size));
return (head - tail - CACHELINE_BYTES) & (size - 1);
}
#endif /* INTEL_RING_H */
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