Having been forced to reduce Braswell back to using the aliasing ppgtt,
the coherency issue we previously observed cannot impact us. Reduce the
performance penalty imposed on all platforms from using the mfence to a
mere sfence.
References: cf66b8a0ba14 ("drm/i915/execlists: Apply a full mb before execution
for Braswell")
Signed-off-by: Chris Wilson <[email protected]>
Cc: Mika Kuoppala <[email protected]>
Cc: Joonas Lahtinen <[email protected]>
---
drivers/gpu/drm/i915/gt/intel_lrc.c | 7 +------
1 file changed, 1 insertion(+), 6 deletions(-)
diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c
b/drivers/gpu/drm/i915/gt/intel_lrc.c
index 1975fe4775d2..e57345795c08 100644
--- a/drivers/gpu/drm/i915/gt/intel_lrc.c
+++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
@@ -1218,13 +1218,8 @@ static u64 execlists_update_context(const struct
i915_request *rq)
* may not be visible to the HW prior to the completion of the UC
* register write and that we may begin execution from the context
* before its image is complete leading to invalid PD chasing.
- *
- * Furthermore, Braswell, at least, wants a full mb to be sure that
- * the writes are coherent in memory (visible to the GPU) prior to
- * execution, and not just visible to other CPUs (as is the result of
- * wmb).
*/
- mb();
+ wmb();
desc = ce->lrc_desc;
ce->lrc_desc &= ~CTX_DESC_FORCE_RESTORE;
--
2.24.0
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