From: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> On Haswell, in particular, 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. References: https://gitlab.freedesktop.org/drm/intel/-/issues/5432 Testcase: igt/i915_selftest/hangcheck Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> Signed-off-by: Nitin Gote <nitin.r.gote@xxxxxxxxx> --- .../gpu/drm/i915/gt/intel_ring_submission.c | 44 +++++++++++++------ drivers/gpu/drm/i915/i915_utils.h | 9 ++++ 2 files changed, 39 insertions(+), 14 deletions(-) diff --git a/drivers/gpu/drm/i915/gt/intel_ring_submission.c b/drivers/gpu/drm/i915/gt/intel_ring_submission.c index 72277bc8322e..6427f07ed23e 100644 --- a/drivers/gpu/drm/i915/gt/intel_ring_submission.c +++ b/drivers/gpu/drm/i915/gt/intel_ring_submission.c @@ -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 +231,20 @@ static int xcs_resume(struct intel_engine_cs *engine) set_pp_dir(engine); /* First wake the ring up to an empty/idle ring */ - ENGINE_WRITE_FW(engine, RING_HEAD, ring->head); + until_timeout_ns(kt, 2 * NSEC_PER_MSEC) { + 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 +253,16 @@ 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) { @@ -259,16 +275,16 @@ static int xcs_resume(struct intel_engine_cs *engine) return 0; err: - drm_err(&engine->i915->drm, - "%s initialization failed; " - "ctl %08x (valid? %d) head %08x [%08x] tail %08x [%08x] start %08x [expected %08x]\n", - engine->name, - ENGINE_READ(engine, RING_CTL), - ENGINE_READ(engine, RING_CTL) & RING_VALID, - ENGINE_READ(engine, RING_HEAD), ring->head, - ENGINE_READ(engine, RING_TAIL), ring->tail, - ENGINE_READ(engine, RING_START), - i915_ggtt_offset(ring->vma)); + ENGINE_TRACE(engine, + "initialization failed; " + "ctl %08x (valid? %d) head %08x [%08x] tail %08x [%08x] start %08x [expected %08x]\n", + ENGINE_READ(engine, RING_CTL), + ENGINE_READ(engine, RING_CTL) & RING_VALID, + ENGINE_READ(engine, RING_HEAD), ring->head, + ENGINE_READ(engine, RING_TAIL), ring->tail, + ENGINE_READ(engine, RING_START), + i915_ggtt_offset(ring->vma)); + GEM_TRACE_DUMP(); return -EIO; } diff --git a/drivers/gpu/drm/i915/i915_utils.h b/drivers/gpu/drm/i915/i915_utils.h index 609214231ffc..538dfb8fa1d8 100644 --- a/drivers/gpu/drm/i915/i915_utils.h +++ b/drivers/gpu/drm/i915/i915_utils.h @@ -232,6 +232,15 @@ wait_remaining_ms_from_jiffies(unsigned long timestamp_jiffies, int to_wait_ms) } } +/* + * until_timeout_ns - Keep retrying (busy spin) until the duration has passed + */ + +#define until_timeout_ns(end, timeout_ns) \ + for ((end) = ktime_get() + (timeout_ns); \ + ktime_before(ktime_get(), (end)); \ + cpu_relax()) + /* * __wait_for - magic wait macro * -- 2.25.1
