Merge branch 'drm-intel-next' of git://anongit.freedesktop.org/drm-intel into drm...

[cascardo/linux.git] / drivers / gpu / drm / drm_irq.c

diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
index 66e5c1e..5a773e4 100644 (file)
--- a/drivers/gpu/drm/drm_irq.c
+++ b/drivers/gpu/drm/drm_irq.c
@@ -242,6 +242,37 @@ static void drm_update_vblank_count(struct drm_device *dev, unsigned int pipe,
        store_vblank(dev, pipe, diff, &t_vblank, cur_vblank);
 }
 
+/**
+ * drm_accurate_vblank_count - retrieve the master vblank counter
+ * @crtc: which counter to retrieve
+ *
+ * This function is similar to @drm_crtc_vblank_count but this
+ * function interpolates to handle a race with vblank irq's.
+ *
+ * This is mostly useful for hardware that can obtain the scanout
+ * position, but doesn't have a frame counter.
+ */
+u32 drm_accurate_vblank_count(struct drm_crtc *crtc)
+{
+       struct drm_device *dev = crtc->dev;
+       unsigned int pipe = drm_crtc_index(crtc);
+       u32 vblank;
+       unsigned long flags;
+
+       WARN(!dev->driver->get_vblank_timestamp,
+            "This function requires support for accurate vblank timestamps.");
+
+       spin_lock_irqsave(&dev->vblank_time_lock, flags);
+
+       drm_update_vblank_count(dev, pipe, 0);
+       vblank = drm_vblank_count(dev, pipe);
+
+       spin_unlock_irqrestore(&dev->vblank_time_lock, flags);
+
+       return vblank;
+}
+EXPORT_SYMBOL(drm_accurate_vblank_count);
+
 /*
  * Disable vblank irq's on crtc, make sure that last vblank count
  * of hardware and corresponding consistent software vblank counter