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drm/i915/selftests: Provide full mb() around clflush 

clflush is an unserialised instruction and the IA manual strongly advises
you to serialise it with a mb. To be cautious, apply one before and one
after, so that it is serialised with both writes and reads without
worrying too much about the required direction.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180706174926.4712-1-chris@chris-wilson.co.uk
This commit is contained in:
Chris Wilson 2018-07-06 18:49:26 +01:00
parent 8b293eb53a
commit 3a32497f0d
1 changed files with 18 additions and 3 deletions
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21
drivers/gpu/drm/i915/selftests/i915_gem_coherency.c
View File

@ -42,11 +42,21 @@ static int cpu_set(struct drm_i915_gem_object *obj,
page = i915_gem_object_get_page(obj, offset >> PAGE_SHIFT);
map = kmap_atomic(page);
if (needs_clflush & CLFLUSH_BEFORE)
if (needs_clflush & CLFLUSH_BEFORE) {
mb();
clflush(map+offset_in_page(offset) / sizeof(*map));
mb();
}
map[offset_in_page(offset) / sizeof(*map)] = v;
if (needs_clflush & CLFLUSH_AFTER)
if (needs_clflush & CLFLUSH_AFTER) {
mb();
clflush(map+offset_in_page(offset) / sizeof(*map));
mb();
}
kunmap_atomic(map);
i915_gem_obj_finish_shmem_access(obj);
@ -68,8 +78,13 @@ static int cpu_get(struct drm_i915_gem_object *obj,
page = i915_gem_object_get_page(obj, offset >> PAGE_SHIFT);
map = kmap_atomic(page);
if (needs_clflush & CLFLUSH_BEFORE)
if (needs_clflush & CLFLUSH_BEFORE) {
mb();
clflush(map+offset_in_page(offset) / sizeof(*map));
mb();
}
*v = map[offset_in_page(offset) / sizeof(*map)];
kunmap_atomic(map);