[Intel-gfx] [PATCH 14/15] drm/i915: Flush idle barriers when waiting

[Chris Wilson]

If we do find ourselves with an idle barrier inside our active while
waiting, attempt to flush it by emitting a pulse using the kernel
context.

Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk>
---
 .../gpu/drm/i915/gt/intel_engine_heartbeat.c  | 14 +++++++++++++
 .../gpu/drm/i915/gt/intel_engine_heartbeat.h  |  1 +
 drivers/gpu/drm/i915/i915_active.c            | 21 +++++++++++++++++--
 3 files changed, 34 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_engine_heartbeat.c 
b/drivers/gpu/drm/i915/gt/intel_engine_heartbeat.c
index dc741e86fb41..f02f660479fa 100644
--- a/drivers/gpu/drm/i915/gt/intel_engine_heartbeat.c
+++ b/drivers/gpu/drm/i915/gt/intel_engine_heartbeat.c
@@ -182,3 +182,17 @@ int intel_engine_pulse(struct intel_engine_cs *engine)
        intel_engine_pm_put(engine);
        return err;
 }
+
+int intel_engine_flush_barriers(struct intel_engine_cs *engine)
+{
+       struct i915_request *rq;
+
+       rq = i915_request_create(engine->kernel_context);
+       if (IS_ERR(rq))
+               return PTR_ERR(rq);
+
+       idle_pulse(engine, rq);
+       i915_request_add(rq);
+
+       return 0;
+}
diff --git a/drivers/gpu/drm/i915/gt/intel_engine_heartbeat.h 
b/drivers/gpu/drm/i915/gt/intel_engine_heartbeat.h
index 39391004554d..0c1ad0fc091d 100644
--- a/drivers/gpu/drm/i915/gt/intel_engine_heartbeat.h
+++ b/drivers/gpu/drm/i915/gt/intel_engine_heartbeat.h
@@ -15,5 +15,6 @@ void intel_engine_park_heartbeat(struct intel_engine_cs 
*engine);
 void intel_engine_unpark_heartbeat(struct intel_engine_cs *engine);
 
 int intel_engine_pulse(struct intel_engine_cs *engine);
+int intel_engine_flush_barriers(struct intel_engine_cs *engine);
 
 #endif /* INTEL_ENGINE_HEARTBEAT_H */
diff --git a/drivers/gpu/drm/i915/i915_active.c 
b/drivers/gpu/drm/i915/i915_active.c
index aa37c07004b9..98d5fe1c7e19 100644
--- a/drivers/gpu/drm/i915/i915_active.c
+++ b/drivers/gpu/drm/i915/i915_active.c
@@ -6,6 +6,7 @@
 
 #include <linux/debugobjects.h>
 
+#include "gt/intel_engine_heartbeat.h"
 #include "gt/intel_engine_pm.h"
 
 #include "i915_drv.h"
@@ -435,6 +436,21 @@ static void enable_signaling(struct i915_active_fence 
*active)
        dma_fence_put(fence);
 }
 
+static int flush_barrier(struct active_node *it)
+{
+       struct intel_engine_cs *engine;
+
+       if (!is_barrier(&it->base))
+               return 0;
+
+       engine = __barrier_to_engine(it);
+       smp_rmb(); /* serialise with add_active_barriers */
+       if (!is_barrier(&it->base))
+               return 0;
+
+       return intel_engine_flush_barriers(engine);
+}
+
 int i915_active_wait(struct i915_active *ref)
 {
        struct active_node *it, *n;
@@ -448,8 +464,9 @@ int i915_active_wait(struct i915_active *ref)
        /* Flush lazy signals */
        enable_signaling(&ref->excl);
        rbtree_postorder_for_each_entry_safe(it, n, &ref->tree, node) {
-               if (is_barrier(&it->base)) /* unconnected idle barrier */
-                       continue;
+               err = flush_barrier(it); /* unconnected idle barrier? */
+               if (err)
+                       break;
 
                enable_signaling(&it->base);
        }
-- 
2.23.0

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