[Intel-gfx] [PATCH 09/11] 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>
---
 drivers/gpu/drm/i915/i915_active.c           | 21 ++++++++-
 drivers/gpu/drm/i915/selftests/i915_active.c | 46 ++++++++++++++++++++
 2 files changed, 65 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_active.c 
b/drivers/gpu/drm/i915/i915_active.c
index 207383dda84d..3e3495838a93 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 "gt/intel_ring.h"
 
@@ -436,6 +437,21 @@ 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;
@@ -449,8 +465,9 @@ 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);
        }
diff --git a/drivers/gpu/drm/i915/selftests/i915_active.c 
b/drivers/gpu/drm/i915/selftests/i915_active.c
index 96513a7d4739..aca107cb6176 100644
--- a/drivers/gpu/drm/i915/selftests/i915_active.c
+++ b/drivers/gpu/drm/i915/selftests/i915_active.c
@@ -193,11 +193,57 @@ static int live_active_retire(void *arg)
        return err;
 }
 
+static int live_active_barrier(void *arg)
+{
+       struct drm_i915_private *i915 = arg;
+       struct intel_engine_cs *engine;
+       struct live_active *active;
+       int err = 0;
+
+       /* Check that we get a callback when requests retire upon waiting */
+
+       active = __live_alloc(i915);
+       if (!active)
+               return -ENOMEM;
+
+       err = i915_active_acquire(&active->base);
+       if (err)
+               goto out;
+
+       for_each_uabi_engine(engine, i915) {
+               err = i915_active_acquire_preallocate_barrier(&active->base,
+                                                             engine);
+               if (err)
+                       break;
+
+               i915_active_acquire_barrier(&active->base);
+       }
+
+       i915_active_release(&active->base);
+
+       if (err == 0)
+               err = i915_active_wait(&active->base);
+
+       if (err == 0 && !READ_ONCE(active->retired)) {
+               pr_err("i915_active not retired after flushing barriers!\n");
+               err = -EINVAL;
+       }
+
+out:
+       __live_put(active);
+
+       if (igt_flush_test(i915))
+               err = -EIO;
+
+       return err;
+}
+
 int i915_active_live_selftests(struct drm_i915_private *i915)
 {
        static const struct i915_subtest tests[] = {
                SUBTEST(live_active_wait),
                SUBTEST(live_active_retire),
+               SUBTEST(live_active_barrier),
        };
 
        if (intel_gt_is_wedged(&i915->gt))
-- 
2.24.0.rc0

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