path: root/include/uapi/drm/i915_drm.h
diff options
authorChris Wilson <>2017-04-12 12:01:11 +0100
committerChris Wilson <>2017-04-12 12:35:17 +0100
commite22d8e3c69a9f432b40baaaf3f894a128fdc2222 (patch)
treef076dadac5c963736a8fe1a25d31013f512d0366 /include/uapi/drm/i915_drm.h
parentef74921bc679232c6590afa881d3ea605ebdddd8 (diff)
drm/i915: Treat WC a separate cache domain
When discussing a new WC mmap, we based the interface upon the assumption that GTT was fully coherent. How naive! Commits 3b5724d702ef ("drm/i915: Wait for writes through the GTT to land before reading back") and ed4596ea992d ("drm/i915/guc: WA to address the Ringbuffer coherency issue") demonstrate that writes through the GTT are indeed delayed and may be overtaken by direct WC access. To be safe, if userspace is mixing WC mmaps with other potential GTT access (pwrite, GTT mmaps) it should use set_domain(WC). Bugzilla: Testcase: igt/gem_pwrite/small-gtt* Testcase: igt/drv_selftest/coherency Signed-off-by: Chris Wilson <> Reviewed-by: Joonas Lahtinen <> Link:
Diffstat (limited to 'include/uapi/drm/i915_drm.h')
1 files changed, 2 insertions, 0 deletions
diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
index 3554495bef13..9ee06ec8a2d6 100644
--- a/include/uapi/drm/i915_drm.h
+++ b/include/uapi/drm/i915_drm.h
@@ -666,6 +666,8 @@ struct drm_i915_gem_relocation_entry {
#define I915_GEM_DOMAIN_VERTEX 0x00000020
/** GTT domain - aperture and scanout */
#define I915_GEM_DOMAIN_GTT 0x00000040
+/** WC domain - uncached access */
+#define I915_GEM_DOMAIN_WC 0x00000080
/** @} */
struct drm_i915_gem_exec_object {