From aa34a6fc2722f042e372741661c0fae8640245ac Mon Sep 17 00:00:00 2001
From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Fri, 24 Nov 2017 13:37:44 +0000
Subject: [PATCH] drm/i915/guc: Advance over port[0] if set and not preempting
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Git-commit: aa34a6fc2722f042e372741661c0fae8640245ac
Patch-mainline: v4.16-rc1
References: FATE#322643 bsc#1055900

Our execlist emulation is intended to only use a maximum of 2 ports per
engine, so as to not overflow the wq. (By knowing the limits, we can
avoid having to handle the wq exhaustion.) However, upon adding
preemption, we lost the skip over the first port if set for the
non-preemption path. Restore it.

Reported-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Fixes: c41937fd994a ("drm/i915/guc: Preemption! With GuC")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Michał Winiarski <michal.winiarski@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171124133745.5173-1-chris@chris-wilson.co.uk
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Michał Winiarski <michal.winiarski@intel.com>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/gpu/drm/i915/intel_guc_submission.c |   27 +++++++++++++++------------
 1 file changed, 15 insertions(+), 12 deletions(-)

--- a/drivers/gpu/drm/i915/intel_guc_submission.c
+++ b/drivers/gpu/drm/i915/intel_guc_submission.c
@@ -743,23 +743,26 @@ static void guc_dequeue(struct intel_eng
 	if (!rb)
 		goto unlock;
 
-	if (HAS_LOGICAL_RING_PREEMPTION(engine->i915) && port_isset(port)) {
-		struct guc_preempt_work *preempt_work =
-			&engine->i915->guc.preempt_work[engine->id];
+	if (port_isset(port)) {
+		if (HAS_LOGICAL_RING_PREEMPTION(engine->i915)) {
+			struct guc_preempt_work *preempt_work =
+				&engine->i915->guc.preempt_work[engine->id];
 
-		if (rb_entry(rb, struct i915_priolist, node)->priority >
-		    max(port_request(port)->priotree.priority, 0)) {
-			execlists_set_active(execlists,
-					     EXECLISTS_ACTIVE_PREEMPT);
-			queue_work(engine->i915->guc.preempt_wq,
-				   &preempt_work->work);
-			goto unlock;
-		} else if (port_isset(last_port)) {
-			goto unlock;
+			if (rb_entry(rb, struct i915_priolist, node)->priority >
+			    max(port_request(port)->priotree.priority, 0)) {
+				execlists_set_active(execlists,
+						     EXECLISTS_ACTIVE_PREEMPT);
+				queue_work(engine->i915->guc.preempt_wq,
+					   &preempt_work->work);
+				goto unlock;
+			}
 		}
 
 		port++;
+		if (port_isset(port))
+			goto unlock;
 	}
+	GEM_BUG_ON(port_isset(port));
 
 	do {
 		struct i915_priolist *p = rb_entry(rb, typeof(*p), node);