drm/imx: only enable vblank IRQs when needed

The vblank IRQ is only needed to trigger page flip work, so we
might as well disable it when there is no work to do.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>

drivers/gpu/drm/imx/ipuv3-crtc.c

@@ -379,11 +379,18 @@ static const struct drm_crtc_helper_funcs ipu_helper_funcs = {
 
 static int ipu_enable_vblank(struct drm_crtc *crtc)
 {
+	struct ipu_crtc *ipu_crtc = to_ipu_crtc(crtc);
+
+	enable_irq(ipu_crtc->irq);
+
 	return 0;
 }
 
 static void ipu_disable_vblank(struct drm_crtc *crtc)
 {
+	struct ipu_crtc *ipu_crtc = to_ipu_crtc(crtc);
+
+	disable_irq_nosync(ipu_crtc->irq);
 }
 
 static int ipu_set_interface_pix_fmt(struct drm_crtc *crtc,
@@ -494,6 +501,8 @@ static int ipu_crtc_init(struct ipu_crtc *ipu_crtc,
 		dev_err(ipu_crtc->dev, "irq request failed with %d.\n", ret);
 		goto err_put_plane_res;
 	}
+	/* Only enable IRQ when we actually need it to trigger work. */
+	disable_irq(ipu_crtc->irq);
 
 	ipu_crtc->flip_queue = create_singlethread_workqueue("ipu-crtc-flip");