drm/i915: Clear fb_tracking.busy_bits also for synchronous flips

The current/old frontbuffer might still have gpu frontbuffer rendering
pending. But once flipped it won't have the corresponding frontbuffer
bits any more and hence the request retire function won't ever clear
the corresponding busy bits. The async flip tracking (with the
flip_prepare and flip_complete functions) already does this, but
somehow I've forgotten to do this for synchronous flips.

Note that we don't track outstanding rendering of the new framebuffer
with busy_bits since all our plane update code waits for previous
rendering to complete before displaying a new buffer. Hence a new
buffer will never be busy.

v2: Drop the spurious inline Ville spotted.

v3: Don't touch flip_bits in the synchronsou frontbuffer_flip
function, noticed by Paulo.

v4: Remove one more inline that slipped through (Paulo).

Reported-by: Paulo Zanoni <przanoni@gmail.com>
Cc: Paulo Zanoni <przanoni@gmail.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Testcase: igt/kms_frontbuffer_tracking/fbc-modesetfrombusy
Tested-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>

drivers/gpu/drm/i915/intel_drv.h

@@ -963,23 +963,8 @@ void intel_frontbuffer_flip_complete(struct drm_device *dev,
 				     unsigned frontbuffer_bits);
 void intel_frontbuffer_flush(struct drm_device *dev,
 			     unsigned frontbuffer_bits);
-/**
- * intel_frontbuffer_flip - synchronous frontbuffer flip
- * @dev: DRM device
- * @frontbuffer_bits: frontbuffer plane tracking bits
- *
- * This function gets called after scheduling a flip on @obj. This is for
- * synchronous plane updates which will happen on the next vblank and which will
- * not get delayed by pending gpu rendering.
- *
- * Can be called without any locks held.
- */
-static inline
 void intel_frontbuffer_flip(struct drm_device *dev,
-			    unsigned frontbuffer_bits)
-{
-	intel_frontbuffer_flush(dev, frontbuffer_bits);
-}
+			    unsigned frontbuffer_bits);
 
 unsigned int intel_fb_align_height(struct drm_device *dev,
 				   unsigned int height,

drivers/gpu/drm/i915/intel_frontbuffer.c

@@ -266,3 +266,28 @@ void intel_frontbuffer_flip_complete(struct drm_device *dev,
 
 	intel_frontbuffer_flush(dev, frontbuffer_bits);
 }
+
+/**
+ * intel_frontbuffer_flip - synchronous frontbuffer flip
+ * @dev: DRM device
+ * @frontbuffer_bits: frontbuffer plane tracking bits
+ *
+ * This function gets called after scheduling a flip on @obj. This is for
+ * synchronous plane updates which will happen on the next vblank and which will
+ * not get delayed by pending gpu rendering.
+ *
+ * Can be called without any locks held.
+ */
+
+void intel_frontbuffer_flip(struct drm_device *dev,
+			    unsigned frontbuffer_bits)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+
+	mutex_lock(&dev_priv->fb_tracking.lock);
+	/* Remove stale busy bits due to the old buffer. */
+	dev_priv->fb_tracking.busy_bits &= ~frontbuffer_bits;
+	mutex_unlock(&dev_priv->fb_tracking.lock);
+
+	intel_frontbuffer_flush(dev, frontbuffer_bits);
+}