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drm/i915/gt: Add delay to let engine resumes properly

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Sometimes engine reset fails because the engine resumes from an
incorrect RING_HEAD. Engine head failed to set to zero even after
writing into it. This is a timing issue and we experimented
different values and found out that 20ms delay works best based
on testing.

So, add a 20ms delay to let engine resumes from correct RING_HEAD.

Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/13968
Signed-off-by: Nitin Gote <nitin.r.gote@intel.com>
Reviewed-by: Sebastian Brzezinka <sebastian.brzezinka@intel.com>
Reviewed-by: Krzysztof Karas <krzysztof.karas@intel.com>
Link: https://lore.kernel.org/r/20250416103640.212269-1-nitin.r.gote@intel.com
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
This commit is contained in:
Nitin Gote 2025-04-16 16:06:40 +05:30 committed by Rodrigo Vivi
parent 795dbde92f
commit ce7743bc1b
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1 changed files with 7 additions and 1 deletions
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8
drivers/gpu/drm/i915/gt/intel_ring_submission.c
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@ -365,7 +365,13 @@ static void reset_prepare(struct intel_engine_cs *engine)
ENGINE_READ_FW(engine, RING_HEAD),
ENGINE_READ_FW(engine, RING_TAIL),
ENGINE_READ_FW(engine, RING_START));
if (!stop_ring(engine)) {
/*
* Sometimes engine head failed to set to zero even after writing into it.
* Use wait_for_atomic() with 20ms delay to let engine resumes from
* correct RING_HEAD. Experimented different values and determined
* that 20ms works best based on testing.
*/
if (wait_for_atomic((!stop_ring(engine) == 0), 20)) {
drm_err(&engine->i915->drm,
"failed to set %s head to zero "
"ctl %08x head %08x tail %08x start %08x\n",