drm/i915: Propagate errors from writing to ringbuffer

Preparing the ringbuffer for adding new commands can fail (a timeout
whilst waiting for the GPU to catch up and free some space). So check
for any potential error before overwriting HEAD with new commands, and
propagate that error back to the user where possible.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

1 files changed, 7 insertions, 6 deletions

diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index 852a2d848bf4..8acdd6d857d3 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -1101,12 +1101,13 @@ static int i915_emit_irq(struct drm_device * dev)
         if (master_priv->sarea_priv)
                 master_priv->sarea_priv->last_enqueue = dev_priv->counter;
 
-        BEGIN_LP_RING(4);
-        OUT_RING(MI_STORE_DWORD_INDEX);
-        OUT_RING(I915_BREADCRUMB_INDEX << MI_STORE_DWORD_INDEX_SHIFT);
-        OUT_RING(dev_priv->counter);
-        OUT_RING(MI_USER_INTERRUPT);
-        ADVANCE_LP_RING();
+        if (BEGIN_LP_RING(4) == 0) {
+                OUT_RING(MI_STORE_DWORD_INDEX);
+                OUT_RING(I915_BREADCRUMB_INDEX << MI_STORE_DWORD_INDEX_SHIFT);
+                OUT_RING(dev_priv->counter);
+                OUT_RING(MI_USER_INTERRUPT);
+                ADVANCE_LP_RING();
+        }
 
         return dev_priv->counter;
 }