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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: 396f5d62d1 ("drm: Restore double clflush on the last partial cacheline")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180730075351.15569-3-chris@chris-wilson.co.uk
This commit is contained in:
Chris Wilson 2018-07-30 08:53:51 +01:00
parent 39f3be162c
commit f6844a85e0
1 changed files with 17 additions and 21 deletions
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38
drivers/gpu/drm/i915/selftests/i915_gem_coherency.c
View File

@ -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 = *cpu;
*v = map[offset_in_page(offset) / sizeof(*map)];
kunmap_atomic(map);
i915_gem_obj_finish_shmem_access(obj);
return 0;
}