2 files changed, 46 insertions, 0 deletions

diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
index 6f16a104d6d0..e64d24951fc2 100644
--- a/drivers/gpu/drm/drm_irq.c
+++ b/drivers/gpu/drm/drm_irq.c
@@ -1010,6 +1010,50 @@ void drm_crtc_vblank_put(struct drm_crtc *crtc)
 EXPORT_SYMBOL(drm_crtc_vblank_put);
 
 /**
+ * drm_wait_one_vblank - wait for one vblank
+ * @dev: DRM device
+ * @crtc: crtc index
+ *
+ * This waits for one vblank to pass on @crtc, using the irq driver interfaces.
+ * It is a failure to call this when the vblank irq for @crtc is disabled, e.g.
+ * due to lack of driver support or because the crtc is off.
+ */
+void drm_wait_one_vblank(struct drm_device *dev, int crtc)
+{
+        int ret;
+        u32 last;
+
+        ret = drm_vblank_get(dev, crtc);
+        if (WARN_ON(ret))
+                return;
+
+        last = drm_vblank_count(dev, crtc);
+
+        ret = wait_event_timeout(dev->vblank[crtc].queue,
+                                 last != drm_vblank_count(dev, crtc),
+                                 msecs_to_jiffies(100));
+
+        WARN_ON(ret == 0);
+
+        drm_vblank_put(dev, crtc);
+}
+EXPORT_SYMBOL(drm_wait_one_vblank);
+
+/**
+ * drm_crtc_wait_one_vblank - wait for one vblank
+ * @crtc: DRM crtc
+ *
+ * This waits for one vblank to pass on @crtc, using the irq driver interfaces.
+ * It is a failure to call this when the vblank irq for @crtc is disabled, e.g.
+ * due to lack of driver support or because the crtc is off.
+ */
+void drm_crtc_wait_one_vblank(struct drm_crtc *crtc)
+{
+        drm_wait_one_vblank(crtc->dev, drm_crtc_index(crtc));
+}
+EXPORT_SYMBOL(drm_crtc_wait_one_vblank);
+
+/**
  * drm_vblank_off - disable vblank events on a CRTC
  * @dev: DRM device
  * @crtc: CRTC in question
diff --git a/include/drm/drmP.h b/include/drm/drmP.h
index d3d9be6b83ef..c2209178981f 100644
--- a/include/drm/drmP.h
+++ b/include/drm/drmP.h
@@ -1327,6 +1327,8 @@ extern int drm_vblank_get(struct drm_device *dev, int crtc);
 extern void drm_vblank_put(struct drm_device *dev, int crtc);
 extern int drm_crtc_vblank_get(struct drm_crtc *crtc);
 extern void drm_crtc_vblank_put(struct drm_crtc *crtc);
+extern void drm_wait_one_vblank(struct drm_device *dev, int crtc);
+extern void drm_crtc_wait_one_vblank(struct drm_crtc *crtc);
 extern void drm_vblank_off(struct drm_device *dev, int crtc);
 extern void drm_vblank_on(struct drm_device *dev, int crtc);
 extern void drm_crtc_vblank_off(struct drm_crtc *crtc);