[PATCH 1/2] drm/imx: disable planes before DC

[Lucas Stach]

If the DC clock is disabled before the attached IDMACs are properly
stopped the IDMACs may hang the IPU or even the whole system.

Make sure the IDMACs are in safe state by disabling the planes before
removal of the DC clock.

Fixes: 33f14235302f (drm/imx: atomic phase 1: Use transitional atomic
                     CRTC and plane helpers)
Signed-off-by: Lucas Stach <l.stach at pengutronix.de>
---
 drivers/gpu/drm/imx/ipuv3-crtc.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/imx/ipuv3-crtc.c b/drivers/gpu/drm/imx/ipuv3-crtc.c
index 4e1ae3fc462d..6be515a9fb69 100644
--- a/drivers/gpu/drm/imx/ipuv3-crtc.c
+++ b/drivers/gpu/drm/imx/ipuv3-crtc.c
@@ -68,6 +68,12 @@ static void ipu_crtc_atomic_disable(struct drm_crtc *crtc,
 
 	ipu_dc_disable_channel(ipu_crtc->dc);
 	ipu_di_disable(ipu_crtc->di);
+	/*
+	 * Planes must be disabled before DC clock is removed, as otherwise the
+	 * attached IDMACs will be left in undefined state, possibly hanging
+	 * the IPU or even system.
+	 */
+	drm_atomic_helper_disable_planes_on_crtc(old_crtc_state, false);
 	ipu_dc_disable(ipu);
 
 	spin_lock_irq(&crtc->dev->event_lock);
@@ -77,9 +83,6 @@ static void ipu_crtc_atomic_disable(struct drm_crtc *crtc,
 	}
 	spin_unlock_irq(&crtc->dev->event_lock);
 
-	/* always disable planes on the CRTC */
-	drm_atomic_helper_disable_planes_on_crtc(old_crtc_state, true);
-
 	drm_crtc_vblank_off(crtc);
 }
 
-- 
2.10.1