Commit 6ef0e3ef authored by Nitin Gote's avatar Nitin Gote Committed by Andi Shyti
Browse files

drm/i915/gt: Retry RING_HEAD reset until it get sticks 

we see an issue where resets fails because the engine resumes
from an incorrect RING_HEAD. Since the RING_HEAD doesn't point
to the remaining requests to re-run, but may instead point into
the uninitialised portion of the ring, the GPU may be then fed
invalid instructions from a privileged context, oft pushing the
GPU into an unrecoverable hang.

If at first the write doesn't succeed, try, try again.

v2: Avoid unnecessary timeout macro (Andi)

v3: Correct comment format (Andi)

v4: Make it generic for all platform as it won't impact (Chris)

Link: https://gitlab.freedesktop.org/drm/intel/-/issues/5432


Testcase: igt/i915_selftest/hangcheck
Signed-off-by: default avatarChris Wilson <chris.p.wilson@linux.intel.com>
Signed-off-by: default avatarNitin Gote <nitin.r.gote@intel.com>
Reviewed-by: default avatarAndi Shyti <andi.shyti@linux.intel.com>
Signed-off-by: default avatarAndi Shyti <andi.shyti@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241015145710.2478599-1-nitin.r.gote@intel.com
parent e217f220

drivers/gpu/drm/i915/gt/intel_ring_submission.c

+27 −4
Original line number Diff line number Diff line
@@ -192,6 +192,7 @@ static bool stop_ring(struct intel_engine_cs *engine) 
static int xcs_resume(struct intel_engine_cs *engine)

{

	struct intel_ring *ring = engine->legacy.ring;

	ktime_t kt;



	ENGINE_TRACE(engine, "ring:{HEAD:%04x, TAIL:%04x}\n",

		     ring->head, ring->tail);
@@ -230,9 +231,27 @@ static int xcs_resume(struct intel_engine_cs *engine) 
	set_pp_dir(engine);



	/* First wake the ring up to an empty/idle ring */

	for ((kt) = ktime_get() + (2 * NSEC_PER_MSEC);

			ktime_before(ktime_get(), (kt)); cpu_relax()) {

		/*

		 * In case of resets fails because engine resumes from

		 * incorrect RING_HEAD and then GPU may be then fed

		 * to invalid instrcutions, which may lead to unrecoverable

		 * hang. So at first write doesn't succeed then try again.

		 */

		ENGINE_WRITE_FW(engine, RING_HEAD, ring->head);

		if (ENGINE_READ_FW(engine, RING_HEAD) == ring->head)

			break;

	}



	ENGINE_WRITE_FW(engine, RING_TAIL, ring->head);

	ENGINE_POSTING_READ(engine, RING_TAIL);

	if (ENGINE_READ_FW(engine, RING_HEAD) != ENGINE_READ_FW(engine, RING_TAIL)) {

		ENGINE_TRACE(engine, "failed to reset empty ring: [%x, %x]: %x\n",

			     ENGINE_READ_FW(engine, RING_HEAD),

			     ENGINE_READ_FW(engine, RING_TAIL),

			     ring->head);

		goto err;

	}



	ENGINE_WRITE_FW(engine, RING_CTL,

			RING_CTL_SIZE(ring->size) | RING_VALID);
@@ -241,12 +260,16 @@ static int xcs_resume(struct intel_engine_cs *engine) 
	if (__intel_wait_for_register_fw(engine->uncore,

					 RING_CTL(engine->mmio_base),

					 RING_VALID, RING_VALID,

					 5000, 0, NULL))

					 5000, 0, NULL)) {

		ENGINE_TRACE(engine, "failed to restart\n");

		goto err;

	}



	if (GRAPHICS_VER(engine->i915) > 2)

	if (GRAPHICS_VER(engine->i915) > 2) {

		ENGINE_WRITE_FW(engine,

				RING_MI_MODE, _MASKED_BIT_DISABLE(STOP_RING));

		ENGINE_POSTING_READ(engine, RING_MI_MODE);

	}



	/* Now awake, let it get started */

	if (ring->tail != ring->head) {