drm/vc4: Send a VBLANK event when disabling a CRTC

VBLANK events are missed when the CRTC is being disabled because the
driver does not wait till the end of the frame before stopping the
HVS and PV blocks. In this case, we should explicitly issue a VBLANK
event if there's one waiting.
Signed-off-by: NBoris Brezillon <boris.brezillon@free-electrons.com>
Reviewed-by: NEric Anholt <eric@anholt.net>
Link: http://patchwork.freedesktop.org/patch/msgid/1497601833-24588-1-git-send-email-boris.brezillon@free-electrons.com

drivers/gpu/drm/vc4/vc4_crtc.c

@@ -518,6 +518,19 @@ static void vc4_crtc_disable(struct drm_crtc *crtc)
 	WARN_ON_ONCE((HVS_READ(SCALER_DISPSTATX(chan)) &
 		      (SCALER_DISPSTATX_FULL | SCALER_DISPSTATX_EMPTY)) !=
 		     SCALER_DISPSTATX_EMPTY);
+
+	/*
+	 * Make sure we issue a vblank event after disabling the CRTC if
+	 * someone was waiting it.
+	 */
+	if (crtc->state->event) {
+		unsigned long flags;
+
+		spin_lock_irqsave(&dev->event_lock, flags);
+		drm_crtc_send_vblank_event(crtc, crtc->state->event);
+		crtc->state->event = NULL;
+		spin_unlock_irqrestore(&dev->event_lock, flags);
+	}
 }
 
 static void vc4_crtc_enable(struct drm_crtc *crtc)