From ce7743bc1b93cd81b5234b8bb9587607af3f6c2a Mon Sep 17 00:00:00 2001 From: Nitin Gote Date: Wed, 16 Apr 2025 16:06:40 +0530 Subject: [PATCH] drm/i915/gt: Add delay to let engine resumes properly 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 Reviewed-by: Sebastian Brzezinka Reviewed-by: Krzysztof Karas Link: https://lore.kernel.org/r/20250416103640.212269-1-nitin.r.gote@intel.com Signed-off-by: Rodrigo Vivi --- drivers/gpu/drm/i915/gt/intel_ring_submission.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/i915/gt/intel_ring_submission.c b/drivers/gpu/drm/i915/gt/intel_ring_submission.c index 458e29d89978d..a93a65c536ecc 100644 --- a/drivers/gpu/drm/i915/gt/intel_ring_submission.c +++ b/drivers/gpu/drm/i915/gt/intel_ring_submission.c @@ -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", -- 2.47.2