]> git.proxmox.com Git - mirror_ubuntu-kernels.git/commit
drm/i915/gt: Perform an arbitration check before busywaiting
authorChris Wilson <chris@chris-wilson.co.uk>
Tue, 12 Jan 2021 10:07:59 +0000 (10:07 +0000)
committerChris Wilson <chris@chris-wilson.co.uk>
Tue, 12 Jan 2021 11:44:55 +0000 (11:44 +0000)
commit49b20dbf7497597070b74e987d52274e8815cfed
tree6aa988e1a636d7aaf1264b83614705d75a8d979d
parent1a51b50c72372dc33b589a2dc72b292a34be23d8
drm/i915/gt: Perform an arbitration check before busywaiting

During igt_reset_nop_engine, it was observed that an unexpected failed
engine reset lead to us busywaiting on the stop-ring semaphore (set
during the reset preparations) on the first request afterwards. There was
no explicit MI_ARB_CHECK in this sequence as the presumption was that
the failed MI_SEMAPHORE_WAIT would itself act as an arbitration point.
It did not in this circumstance, so force it.

This patch is based on the assumption that the MI_SEMAPHORE_WAIT failure
to arbitrate is a rare Tigerlake bug, similar to the lite-restore vs
semaphore issues previously seen in the CS. The explicit MI_ARB_CHECK
should always ensure that there is at least one arbitration point in the
request before the MI_SEMAPHORE_WAIT to trigger the IDLE->ACTIVE event.
Upon processing that event, we will clear the stop-ring flag and release
the semaphore from its busywait.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210112100759.32698-2-chris@chris-wilson.co.uk
drivers/gpu/drm/i915/gt/gen8_engine_cs.c