3 files changed, 36 insertions, 3 deletions

diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
index 75647e7f012b..e78a1f5cad9c 100644
--- a/drivers/gpu/drm/drm_irq.c
+++ b/drivers/gpu/drm/drm_irq.c
@@ -1226,6 +1226,38 @@ void drm_crtc_vblank_off(struct drm_crtc *crtc)
 EXPORT_SYMBOL(drm_crtc_vblank_off);
 
 /**
+ * drm_crtc_vblank_reset - reset vblank state to off on a CRTC
+ * @crtc: CRTC in question
+ *
+ * Drivers can use this function to reset the vblank state to off at load time.
+ * Drivers should use this together with the drm_crtc_vblank_off() and
+ * drm_crtc_vblank_on() functions. The difference compared to
+ * drm_crtc_vblank_off() is that this function doesn't save the vblank counter
+ * and hence doesn't need to call any driver hooks.
+ */
+void drm_crtc_vblank_reset(struct drm_crtc *drm_crtc)
+{
+        struct drm_device *dev = drm_crtc->dev;
+        unsigned long irqflags;
+        int crtc = drm_crtc_index(drm_crtc);
+        struct drm_vblank_crtc *vblank = &dev->vblank[crtc];
+
+        spin_lock_irqsave(&dev->vbl_lock, irqflags);
+        /*
+         * Prevent subsequent drm_vblank_get() from enabling the vblank
+         * interrupt by bumping the refcount.
+         */
+        if (!vblank->inmodeset) {
+                atomic_inc(&vblank->refcount);
+                vblank->inmodeset = 1;
+        }
+        spin_unlock_irqrestore(&dev->vbl_lock, irqflags);
+
+        WARN_ON(!list_empty(&dev->vblank_event_list));
+}
+EXPORT_SYMBOL(drm_crtc_vblank_reset);
+
+/**
  * drm_vblank_on - enable vblank events on a CRTC
  * @dev: DRM device
  * @crtc: CRTC in question
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 3b0fe9f1f3c9..b901b00a8f2e 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -13316,11 +13316,11 @@ static void intel_sanitize_crtc(struct intel_crtc *crtc)
         I915_WRITE(reg, I915_READ(reg) & ~PIPECONF_FRAME_START_DELAY_MASK);
 
         /* restore vblank interrupts to correct state */
+        drm_crtc_vblank_reset(&crtc->base);
         if (crtc->active) {
                 update_scanline_offset(crtc);
-                drm_vblank_on(dev, crtc->pipe);
-        } else
-                drm_vblank_off(dev, crtc->pipe);
+                drm_crtc_vblank_on(&crtc->base);
+        }
 
         /* We need to sanitize the plane -> pipe mapping first because this will
          * disable the crtc (and hence change the state) if it is wrong. Note
diff --git a/include/drm/drmP.h b/include/drm/drmP.h
index e928625a9da0..54c6ea1e5866 100644
--- a/include/drm/drmP.h
+++ b/include/drm/drmP.h
@@ -922,6 +922,7 @@ 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);
+extern void drm_crtc_vblank_reset(struct drm_crtc *crtc);
 extern void drm_crtc_vblank_on(struct drm_crtc *crtc);
 extern void drm_vblank_cleanup(struct drm_device *dev);