drm/i915/execlists: Apply a full mb before execution for Braswell
authorChris Wilson <chris@chris-wilson.co.uk>
Thu, 6 Dec 2018 08:44:31 +0000 (08:44 +0000)
committerJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Wed, 12 Dec 2018 07:06:14 +0000 (09:06 +0200)
commitcf66b8a0ba142fbd1bf10ac8f3ae92d1b0cb7b8f
tree3f716f4e7c6ff1fb5a35385cfa518136af35e1a3
parentd76b21ebf8ff0ec5030e98c64c50dca2254474f3
drm/i915/execlists: Apply a full mb before execution for Braswell

Braswell is really picky about having our writes posted to memory before
we execute or else the GPU may see stale values. A wmb() is insufficient
as it only ensures the writes are visible to other cores, we need a full
mb() to ensure the writes are in memory and visible to the GPU.

The most frequent failure in flushing before execution is that we see
stale PTE values and execute the wrong pages.

References: 987abd5c62f9 ("drm/i915/execlists: Force write serialisation into context image vs execution")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: stable@vger.kernel.org
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181206084431.9805-3-chris@chris-wilson.co.uk
(cherry picked from commit 490b8c65b9db45896769e1095e78725775f47b3e)
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
drivers/gpu/drm/i915/intel_lrc.c