i915_gem_clflush.c

  1// SPDX-License-Identifier: MIT
  2/*
  3 * Copyright © 2016 Intel Corporation
  4 */
  5
  6#include <drm/drm_cache.h>
  7
  8#include "i915_config.h"
  9#include "i915_drv.h"
 10#include "i915_gem_clflush.h"
 11#include "i915_gem_object_frontbuffer.h"
 12#include "i915_sw_fence_work.h"
 13#include "i915_trace.h"
 14
 15struct clflush {
 16	struct dma_fence_work base;
 17	struct drm_i915_gem_object *obj;
 18};
 19
 20static void __do_clflush(struct drm_i915_gem_object *obj)
 21{
 22	GEM_BUG_ON(!i915_gem_object_has_pages(obj));
 23	drm_clflush_sg(obj->mm.pages);
 24
 25	i915_gem_object_flush_frontbuffer(obj, ORIGIN_CPU);
 26}
 27
 28static void clflush_work(struct dma_fence_work *base)
 29{
 30	struct clflush *clflush = container_of(base, typeof(*clflush), base);
 31
 32	__do_clflush(clflush->obj);
 33}
 34
 35static void clflush_release(struct dma_fence_work *base)
 36{
 37	struct clflush *clflush = container_of(base, typeof(*clflush), base);
 38
 39	i915_gem_object_unpin_pages(clflush->obj);
 40	i915_gem_object_put(clflush->obj);
 41}
 42
 43static const struct dma_fence_work_ops clflush_ops = {
 44	.name = "clflush",
 45	.work = clflush_work,
 46	.release = clflush_release,
 47};
 48
 49static struct clflush *clflush_work_create(struct drm_i915_gem_object *obj)
 50{
 51	struct clflush *clflush;
 52
 53	GEM_BUG_ON(!obj->cache_dirty);
 54
 55	clflush = kmalloc(sizeof(*clflush), GFP_KERNEL);
 56	if (!clflush)
 57		return NULL;
 58
 59	if (__i915_gem_object_get_pages(obj) < 0) {
 60		kfree(clflush);
 61		return NULL;
 62	}
 63
 64	dma_fence_work_init(&clflush->base, &clflush_ops);
 65	clflush->obj = i915_gem_object_get(obj); /* obj <-> clflush cycle */
 66
 67	return clflush;
 68}
 69
 70bool i915_gem_clflush_object(struct drm_i915_gem_object *obj,
 71			     unsigned int flags)
 72{
 73	struct drm_i915_private *i915 = to_i915(obj->base.dev);
 74	struct clflush *clflush;
 75
 76	assert_object_held(obj);
 77
 78	if (IS_DGFX(i915)) {
 79		WARN_ON_ONCE(obj->cache_dirty);
 80		return false;
 81	}
 82
 83	/*
 84	 * Stolen memory is always coherent with the GPU as it is explicitly
 85	 * marked as wc by the system, or the system is cache-coherent.
 86	 * Similarly, we only access struct pages through the CPU cache, so
 87	 * anything not backed by physical memory we consider to be always
 88	 * coherent and not need clflushing.
 89	 */
 90	if (!i915_gem_object_has_struct_page(obj)) {
 91		obj->cache_dirty = false;
 92		return false;
 93	}
 94
 95	/* If the GPU is snooping the contents of the CPU cache,
 96	 * we do not need to manually clear the CPU cache lines.  However,
 97	 * the caches are only snooped when the render cache is
 98	 * flushed/invalidated.  As we always have to emit invalidations
 99	 * and flushes when moving into and out of the RENDER domain, correct
100	 * snooping behaviour occurs naturally as the result of our domain
101	 * tracking.
102	 */
103	if (!(flags & I915_CLFLUSH_FORCE) &&
104	    obj->cache_coherent & I915_BO_CACHE_COHERENT_FOR_READ)
105		return false;
106
107	trace_i915_gem_object_clflush(obj);
108
109	clflush = NULL;
110	if (!(flags & I915_CLFLUSH_SYNC) &&
111	    dma_resv_reserve_fences(obj->base.resv, 1) == 0)
112		clflush = clflush_work_create(obj);
113	if (clflush) {
114		i915_sw_fence_await_reservation(&clflush->base.chain,
115						obj->base.resv, true,
116						i915_fence_timeout(i915),
117						I915_FENCE_GFP);
118		dma_resv_add_fence(obj->base.resv, &clflush->base.dma,
119				   DMA_RESV_USAGE_KERNEL);
120		dma_fence_work_commit(&clflush->base);
121		/*
122		 * We must have successfully populated the pages(since we are
123		 * holding a pin on the pages as per the flush worker) to reach
124		 * this point, which must mean we have already done the required
125		 * flush-on-acquire, hence resetting cache_dirty here should be
126		 * safe.
127		 */
128		obj->cache_dirty = false;
129	} else if (obj->mm.pages) {
130		__do_clflush(obj);
131		obj->cache_dirty = false;
132	} else {
133		GEM_BUG_ON(obj->write_domain != I915_GEM_DOMAIN_CPU);
134	}
135
136	return true;
137}