[Intel-gfx] [PATCH 12/51] drm/i915/guc: Ensure request ordering via completion fences

Matthew Brost
2021-07-16T20:00:14Z

If two requests are on the same ring, they are explicitly ordered by the
HW. So, a submission fence is sufficient to ensure ordering when using
the new GuC submission interface. Conversely, if two requests share a
timeline and are on the same physical engine but different context this
doesn't ensure ordering on the new GuC submission interface. So, a
completion fence needs to be used to ensure ordering.

Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
---
drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c | 1 -
drivers/gpu/drm/i915/i915_request.c | 12 ++++++++++--
2 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
index 9dc1a256e185..4443cc6f5320 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
+++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
@@ -933,7 +933,6 @@ static void guc_context_sched_disable(struct intel_context *ce)
* a request before we set the 'context_pending_disable' flag here.
*/
if (unlikely(atomic_add_unless(&ce->pin_count, -2, 2))) {
- spin_unlock_irqrestore(&ce->guc_state.lock, flags);
return;
}
guc_id = prep_context_pending_disable(ce);
diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c
index b48c4905d3fc..2b2b63cba06c 100644
--- a/drivers/gpu/drm/i915/i915_request.c
+++ b/drivers/gpu/drm/i915/i915_request.c
@@ -432,6 +432,7 @@ void i915_request_retire_upto(struct i915_request *rq)

do {
tmp = list_first_entry(&tl->requests, typeof(*tmp), link);
+ GEM_BUG_ON(!i915_request_completed(tmp));
} while (i915_request_retire(tmp) && tmp != rq);
}

@@ -1380,6 +1381,9 @@ i915_request_await_external(struct i915_request *rq, struct dma_fence *fence)
return err;
}

+static int
+i915_request_await_request(struct i915_request *to, struct i915_request *from);
+
int
i915_request_await_execution(struct i915_request *rq,
struct dma_fence *fence)
@@ -1465,7 +1469,8 @@ i915_request_await_request(struct i915_request *to, struct i915_request *from)
return ret;
}

- if (is_power_of_2(to->execution_mask | READ_ONCE(from->execution_mask)))
+ if (!intel_engine_uses_guc(to->engine) &&
+ is_power_of_2(to->execution_mask | READ_ONCE(from->execution_mask)))
ret = await_request_submit(to, from);
else
ret = emit_semaphore_wait(to, from, I915_FENCE_GFP);
@@ -1626,6 +1631,8 @@ __i915_request_add_to_timeline(struct i915_request *rq)
prev = to_request(__i915_active_fence_set(&timeline->last_request,
&rq->fence));
if (prev && !__i915_request_is_complete(prev)) {
+ bool uses_guc = intel_engine_uses_guc(rq->engine);
+
/*
* The requests are supposed to be kept in order. However,
* we need to be wary in case the timeline->last_request
@@ -1636,7 +1643,8 @@ __i915_request_add_to_timeline(struct i915_request *rq)
i915_seqno_passed(prev->fence.seqno,
rq->fence.seqno));

- if (is_power_of_2(READ_ONCE(prev->engine)->mask | rq->engine->mask))
+ if ((!uses_guc && is_power_of_2(READ_ONCE(prev->engine)->mask | rq->engine->mask)) ||
+ (uses_guc && prev->context == rq->context))
i915_sw_fence_await_sw_fence(&rq->submit,
&prev->submit,
&rq->submitq);
--
2.28.0