[PATCH 25/27] drm/i915/guc: Handle errors in multi-lrc requests

[Matthew Brost <matthew.brost@intel.com>]

If an error occurs in the front end when multi-lrc requests are getting
generated we need to skip these in the backend but we still need to
emit the breadcrumbs seqno. An issues arrises because with multi-lrc
breadcrumbs there is a handshake between the parent and children to make
forwad progress. If all the requests are not present this handshake
doesn't work. To work around this, if multi-lrc request has an error we
skip the handshake but still emit the breadcrumbs seqno.

Signed-off-by: Matthew Brost <matthew.brost@intel.com>
---
 .../gpu/drm/i915/gt/uc/intel_guc_submission.c | 61 ++++++++++++++++++-
 1 file changed, 58 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 2ef38557b0f0..61e737fd1eee 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
+++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
@@ -3546,8 +3546,8 @@ static int emit_bb_start_child_no_preempt_mid_batch(struct i915_request *rq,
 }
 
 static u32 *
-emit_fini_breadcrumb_parent_no_preempt_mid_batch(struct i915_request *rq,
-						 u32 *cs)
+__emit_fini_breadcrumb_parent_no_preempt_mid_batch(struct i915_request *rq,
+						   u32 *cs)
 {
 	struct intel_context *ce = rq->context;
 	u8 i;
@@ -3575,6 +3575,41 @@ emit_fini_breadcrumb_parent_no_preempt_mid_batch(struct i915_request *rq,
 				  get_children_go_addr(ce),
 				  0);
 
+	return cs;
+}
+
+/*
+ * If this true, a submission of multi-lrc requests had an error and the
+ * requests need to be skipped. The front end (execuf IOCTL) should've called
+ * i915_request_skip which squashes the BB but we still need to emit the fini
+ * breadrcrumbs seqno write. At this point we don't know how many of the
+ * requests in the multi-lrc submission were generated so we can't do the
+ * handshake between the parent and children (e.g. if 4 requests should be
+ * generated but 2nd hit an error only 1 would be seen by the GuC backend).
+ * Simply skip the handshake, but still emit the breadcrumbd seqno, if an error
+ * has occurred on any of the requests in submission / relationship.
+ */
+static inline bool skip_handshake(struct i915_request *rq)
+{
+	return test_bit(I915_FENCE_FLAG_SKIP_PARALLEL, &rq->fence.flags);
+}
+
+static u32 *
+emit_fini_breadcrumb_parent_no_preempt_mid_batch(struct i915_request *rq,
+						 u32 *cs)
+{
+	struct intel_context *ce = rq->context;
+
+	GEM_BUG_ON(!intel_context_is_parent(ce));
+
+	if (unlikely(skip_handshake(rq))) {
+		memset(cs, 0, sizeof(u32) *
+		       (ce->engine->emit_fini_breadcrumb_dw - 6));
+		cs += ce->engine->emit_fini_breadcrumb_dw - 6;
+	} else {
+		cs = __emit_fini_breadcrumb_parent_no_preempt_mid_batch(rq, cs);
+	}
+
 	/* Emit fini breadcrumb */
 	cs = gen8_emit_ggtt_write(cs,
 				  rq->fence.seqno,
@@ -3591,7 +3626,8 @@ emit_fini_breadcrumb_parent_no_preempt_mid_batch(struct i915_request *rq,
 }
 
 static u32 *
-emit_fini_breadcrumb_child_no_preempt_mid_batch(struct i915_request *rq, u32 *cs)
+__emit_fini_breadcrumb_child_no_preempt_mid_batch(struct i915_request *rq,
+						  u32 *cs)
 {
 	struct intel_context *ce = rq->context;
 
@@ -3617,6 +3653,25 @@ emit_fini_breadcrumb_child_no_preempt_mid_batch(struct i915_request *rq, u32 *cs
 	*cs++ = get_children_go_addr(ce->parent);
 	*cs++ = 0;
 
+	return cs;
+}
+
+static u32 *
+emit_fini_breadcrumb_child_no_preempt_mid_batch(struct i915_request *rq,
+						u32 *cs)
+{
+	struct intel_context *ce = rq->context;
+
+	GEM_BUG_ON(!intel_context_is_child(ce));
+
+	if (unlikely(skip_handshake(rq))) {
+		memset(cs, 0, sizeof(u32) *
+		       (ce->engine->emit_fini_breadcrumb_dw - 6));
+		cs += ce->engine->emit_fini_breadcrumb_dw - 6;
+	} else {
+		cs = __emit_fini_breadcrumb_child_no_preempt_mid_batch(rq, cs);
+	}
+
 	/* Emit fini breadcrumb */
 	cs = gen8_emit_ggtt_write(cs,
 				  rq->fence.seqno,
-- 
2.32.0