Commit f6844a85 authored by Chris Wilson's avatar Chris Wilson
Browse files

drm/i915/selftests: Replace opencoded clflush with drm_clflush_virt_range 



We occasionally see that the clflush prior to a read of GPU data is
returning stale data, reminiscent of much earlier bugs fixed by adding a
second clflush for serialisation. As drm_clflush_virt_range() already
supplies the workaround, use it rather than open code the clflush
instruction.

References: 396f5d62 ("drm: Restore double clflush on the last partial cacheline")
Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: default avatarMatthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180730075351.15569-3-chris@chris-wilson.co.uk
parent 39f3be16

drivers/gpu/drm/i915/selftests/i915_gem_coherency.c

+17 −21
Original line number Diff line number Diff line
@@ -33,7 +33,8 @@ static int cpu_set(struct drm_i915_gem_object *obj, 
{

	unsigned int needs_clflush;

	struct page *page;

	u32 *map;

	void *map;

	u32 *cpu;

	int err;



	err = i915_gem_obj_prepare_shmem_write(obj, &needs_clflush);
@@ -42,24 +43,19 @@ static int cpu_set(struct drm_i915_gem_object *obj, 


	page = i915_gem_object_get_page(obj, offset >> PAGE_SHIFT);

	map = kmap_atomic(page);

	cpu = map + offset_in_page(offset);



	if (needs_clflush & CLFLUSH_BEFORE) {

		mb();

		clflush(map+offset_in_page(offset) / sizeof(*map));

		mb();

	}

	if (needs_clflush & CLFLUSH_BEFORE)

		drm_clflush_virt_range(cpu, sizeof(*cpu));



	map[offset_in_page(offset) / sizeof(*map)] = v;

	*cpu = v;



	if (needs_clflush & CLFLUSH_AFTER) {

		mb();

		clflush(map+offset_in_page(offset) / sizeof(*map));

		mb();

	}

	if (needs_clflush & CLFLUSH_AFTER)

		drm_clflush_virt_range(cpu, sizeof(*cpu));



	kunmap_atomic(map);



	i915_gem_obj_finish_shmem_access(obj);



	return 0;

}
@@ -69,7 +65,8 @@ static int cpu_get(struct drm_i915_gem_object *obj, 
{

	unsigned int needs_clflush;

	struct page *page;

	u32 *map;

	void *map;

	u32 *cpu;

	int err;



	err = i915_gem_obj_prepare_shmem_read(obj, &needs_clflush);
@@ -78,17 +75,16 @@ static int cpu_get(struct drm_i915_gem_object *obj, 


	page = i915_gem_object_get_page(obj, offset >> PAGE_SHIFT);

	map = kmap_atomic(page);

	cpu = map + offset_in_page(offset);



	if (needs_clflush & CLFLUSH_BEFORE) {

		mb();

		clflush(map+offset_in_page(offset) / sizeof(*map));

		mb();

	}

	if (needs_clflush & CLFLUSH_BEFORE)

		drm_clflush_virt_range(cpu, sizeof(*cpu));



	*v = map[offset_in_page(offset) / sizeof(*map)];

	kunmap_atomic(map);

	*v = *cpu;



	kunmap_atomic(map);

	i915_gem_obj_finish_shmem_access(obj);



	return 0;

}

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