drm/i915: Clear flushing lists on GPU reset

Owain Ainsworth noticed that the reset code failed to clear the flushing
list leaving the driver in an inconsistent state following a hung GPU.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

drivers/gpu/drm/i915/i915_drv.c

@@ -385,6 +385,12 @@ int i965_reset(struct drm_device *dev, u8 flags)
 	 */
 	i915_gem_retire_requests(dev);
 
+	/* Remove anything from the flushing lists. The GPU cache is likely
+	 * to be lost on reset along with the data, so simply move the
+	 * lost bo to the inactive list.
+	 */
+	i915_gem_reset_flushing_list(dev);
+
 	/*
 	 * Set the domains we want to reset (GRDOM/bits 2 and 3) as
 	 * well as the reset bit (GR/bit 0).  Setting the GR bit

drivers/gpu/drm/i915/i915_drv.h

@@ -997,6 +997,7 @@ int i915_gem_object_get_fence_reg(struct drm_gem_object *obj,
 int i915_gem_object_put_fence_reg(struct drm_gem_object *obj,
 				  bool interruptible);
 void i915_gem_retire_requests(struct drm_device *dev);
+void i915_gem_reset_flushing_list(struct drm_device *dev);
 void i915_gem_clflush_object(struct drm_gem_object *obj);
 int i915_gem_object_set_domain(struct drm_gem_object *obj,
 			       uint32_t read_domains,

drivers/gpu/drm/i915/i915_gem.c

@@ -1683,6 +1683,22 @@ i915_get_gem_seqno(struct drm_device *dev,
 	return ring->get_gem_seqno(dev, ring);
 }
 
+void i915_gem_reset_flushing_list(struct drm_device *dev)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+
+	while (!list_empty(&dev_priv->mm.flushing_list)) {
+		struct drm_i915_gem_object *obj_priv;
+
+		obj_priv = list_first_entry(&dev_priv->mm.flushing_list,
+					    struct drm_i915_gem_object,
+					    list);
+
+		obj_priv->base.write_domain = 0;
+		i915_gem_object_move_to_inactive(&obj_priv->base);
+	}
+}
+
 /**
  * This function clears the request list as sequence numbers are passed.
  */