From f6844a85e0c96a55c61fa3e611f414999b11e4de Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Mon, 30 Jul 2018 08:53:51 +0100 Subject: [PATCH] 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: 396f5d62d1a5 ("drm: Restore double clflush on the last partial cacheline") Signed-off-by: Chris Wilson Reviewed-by: Matthew Auld Link: https://patchwork.freedesktop.org/patch/msgid/20180730075351.15569-3-chris@chris-wilson.co.uk --- .../gpu/drm/i915/selftests/i915_gem_coherency.c | 38 ++++++++++------------ 1 file changed, 17 insertions(+), 21 deletions(-) diff --git a/drivers/gpu/drm/i915/selftests/i915_gem_coherency.c b/drivers/gpu/drm/i915/selftests/i915_gem_coherency.c index 3a095c3..4e6a221 100644 --- a/drivers/gpu/drm/i915/selftests/i915_gem_coherency.c +++ b/drivers/gpu/drm/i915/selftests/i915_gem_coherency.c @@ -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; } -- 2.7.4