drm/i915: Use atomics to manipulate obj->frontbuffer_bits

The individual bits inside obj->frontbuffer_bits are protected by each
plane->mutex, but the whole bitfield may be accessed by multiple KMS
operations simultaneously and so the RMW need to be under atomics.
However, for updating the single field we do not need to mandate that it
be under the struct_mutex, one more step towards its removal as the de
facto BKL.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1470324762-2545-21-git-send-email-chris@chris-wilson.co.uk

1 files changed, 9 insertions, 14 deletions

diff --git a/drivers/gpu/drm/i915/intel_frontbuffer.c b/drivers/gpu/drm/i915/intel_frontbuffer.c
index f15486aee7f8..0e5da902473c 100644
--- a/drivers/gpu/drm/i915/intel_frontbuffer.c
+++ b/drivers/gpu/drm/i915/intel_frontbuffer.c
@@ -67,23 +67,22 @@
 #include "i915_drv.h"
 
 void __intel_fb_obj_invalidate(struct drm_i915_gem_object *obj,
-			       enum fb_op_origin origin)
+			       enum fb_op_origin origin,
+			       unsigned int frontbuffer_bits)
 {
 	struct drm_device *dev = obj->base.dev;
 	struct drm_i915_private *dev_priv = to_i915(dev);
 
-	WARN_ON(!mutex_is_locked(&dev->struct_mutex));
-
 	if (origin == ORIGIN_CS) {
 		spin_lock(&dev_priv->fb_tracking.lock);
-		dev_priv->fb_tracking.busy_bits |= obj->frontbuffer_bits;
-		dev_priv->fb_tracking.flip_bits &= ~obj->frontbuffer_bits;
+		dev_priv->fb_tracking.busy_bits |= frontbuffer_bits;
+		dev_priv->fb_tracking.flip_bits &= ~frontbuffer_bits;
 		spin_unlock(&dev_priv->fb_tracking.lock);
 	}
 
-	intel_psr_invalidate(dev, obj->frontbuffer_bits);
-	intel_edp_drrs_invalidate(dev, obj->frontbuffer_bits);
-	intel_fbc_invalidate(dev_priv, obj->frontbuffer_bits, origin);
+	intel_psr_invalidate(dev, frontbuffer_bits);
+	intel_edp_drrs_invalidate(dev, frontbuffer_bits);
+	intel_fbc_invalidate(dev_priv, frontbuffer_bits, origin);
 }
 
 /**
@@ -119,15 +118,11 @@ static void intel_frontbuffer_flush(struct drm_device *dev,
 
 void __intel_fb_obj_flush(struct drm_i915_gem_object *obj,
 			  bool retire,
-			  enum fb_op_origin origin)
+			  enum fb_op_origin origin,
+			  unsigned int frontbuffer_bits)
 {
 	struct drm_device *dev = obj->base.dev;
 	struct drm_i915_private *dev_priv = to_i915(dev);
-	unsigned frontbuffer_bits;
-
-	WARN_ON(!mutex_is_locked(&dev->struct_mutex));
-
-	frontbuffer_bits = obj->frontbuffer_bits;
 
 	if (retire) {
 		spin_lock(&dev_priv->fb_tracking.lock);