Be paranoid and make sure we flush any and all writes out of the WCB before performing the UC mmio to update the RING_TAIL. (An UC write should itself be enough to do the flush, hence the paranoia here.) Quite infrequently, we see problems where the GPU seems to overshoot the RING_TAIL and so executes garbage hence the speculation.
References: https://bugs.freedesktop.org/show_bug.cgi?id=111598 References: https://bugs.freedesktop.org/show_bug.cgi?id=111417 References: https://bugs.freedesktop.org/show_bug.cgi?id=111034 Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk> --- drivers/gpu/drm/i915/gt/intel_ringbuffer.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/gpu/drm/i915/gt/intel_ringbuffer.c b/drivers/gpu/drm/i915/gt/intel_ringbuffer.c index bbda85dcaa42..73c3ffc80218 100644 --- a/drivers/gpu/drm/i915/gt/intel_ringbuffer.c +++ b/drivers/gpu/drm/i915/gt/intel_ringbuffer.c @@ -930,6 +930,7 @@ static void cancel_requests(struct intel_engine_cs *engine) static void i9xx_submit_request(struct i915_request *request) { i915_request_submit(request); + wmb(); /* paranoid flush writes out of the WCB before mmio */ ENGINE_WRITE(request->engine, RING_TAIL, intel_ring_set_tail(request->ring, request->tail)); -- 2.23.0 _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx
