[Intel-gfx] [PATCH 1/4] drm/i915: Only disable execlist preemption for the duration of the request

[Chris Wilson]

We need to prevent resubmission of the context immediately following an
initial resubmit (which does a lite-restore preemption). Currently we do
this by disabling all submission whilst the context is still active, but
we can improve this by limiting the restriction to only until we
receive notification from the context-switch interrupt that the
lite-restore preemption is complete.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/i915_debugfs.c     | 18 ++++++++++++------
 drivers/gpu/drm/i915/intel_lrc.c        |  7 +++----
 drivers/gpu/drm/i915/intel_ringbuffer.h |  1 -
 3 files changed, 15 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index fa69d72fdcb9..9d7a77ecec3d 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -3320,15 +3320,21 @@ static int i915_engine_info(struct seq_file *m, void *unused)
 
 			rcu_read_lock();
 			rq = READ_ONCE(engine->execlist_port[0].request);
-			if (rq)
-				print_request(m, rq, "\t\tELSP[0] ");
-			else
+			if (rq) {
+				seq_printf(m, "\t\tELSP[0] count=%d, ",
+					   engine->execlist_port[0].count);
+				print_request(m, rq, "rq: ");
+			} else {
 				seq_printf(m, "\t\tELSP[0] idle\n");
+			}
 			rq = READ_ONCE(engine->execlist_port[1].request);
-			if (rq)
-				print_request(m, rq, "\t\tELSP[1] ");
-			else
+			if (rq) {
+				seq_printf(m, "\t\tELSP[1] count=%d, ",
+					   engine->execlist_port[1].count);
+				print_request(m, rq, "rq: ");
+			} else {
 				seq_printf(m, "\t\tELSP[1] idle\n");
+			}
 			rcu_read_unlock();
 
 			spin_lock_irq(&engine->timeline->lock);
diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index 432ee495dec2..706b6596ada6 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -388,7 +388,7 @@ static void execlists_submit_ports(struct intel_engine_cs *engine)
 		execlists_context_status_change(port[0].request,
 						INTEL_CONTEXT_SCHEDULE_IN);
 	desc[0] = execlists_update_context(port[0].request);
-	engine->preempt_wa = port[0].count++; /* bdw only? fixed on skl? */
+	port[0].count++;
 
 	if (port[1].request) {
 		GEM_BUG_ON(port[1].count);
@@ -558,7 +558,8 @@ static bool execlists_elsp_ready(struct intel_engine_cs *engine)
 	int port;
 
 	port = 1; /* wait for a free slot */
-	if (engine->disable_lite_restore_wa || engine->preempt_wa)
+	if (engine->disable_lite_restore_wa ||
+	    engine->execlist_port[0].count > 1)
 		port = 0; /* wait for GPU to be idle before continuing */
 
 	return !engine->execlist_port[port].request;
@@ -604,8 +605,6 @@ static void intel_lrc_irq_handler(unsigned long data)
 				i915_gem_request_put(port[0].request);
 				port[0] = port[1];
 				memset(&port[1], 0, sizeof(port[1]));
-
-				engine->preempt_wa = false;
 			}
 
 			GEM_BUG_ON(port[0].count == 0 &&
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
index 79c2b8d72322..34cdbb6350a8 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.h
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
@@ -381,7 +381,6 @@ struct intel_engine_cs {
 	struct rb_node *execlist_first;
 	unsigned int fw_domains;
 	bool disable_lite_restore_wa;
-	bool preempt_wa;
 	u32 ctx_desc_template;
 
 	/* Contexts are pinned whilst they are active on the GPU. The last
-- 
2.11.0