drm/fsl-dcu: disable planes before disabling CRTC

After disabling and reenabling the CRTC the DCU sometimes got stuck
displaying the whole screen with a solid color. Disabling and
reenabling the CRTC did not recover from the situation. This was
often reproducable by just restarting the X-Server.

The disabling sequence is not explicitly documented. But it turns
out that disabling the planes before disabling the CRTC seems to
prevent the above situation from happening.

Use the callback ->atomic_disable instead of ->disable which allows
to use the drm_atomic_helper_disable_planes_on_crtc() helper to
disable planes before disabling the controller.

Signed-off-by: Stefan Agner <stefan@agner.ch>

1 files changed, 6 insertions, 2 deletions

diff --git a/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_crtc.c b/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_crtc.c
index 2ea9dbd9be30..deb57435cc89 100644
--- a/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_crtc.c
+++ b/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_crtc.c
@@ -44,11 +44,15 @@ static void fsl_dcu_drm_crtc_atomic_flush(struct drm_crtc *crtc,
         }
 }
 
-static void fsl_dcu_drm_disable_crtc(struct drm_crtc *crtc)
+static void fsl_dcu_drm_crtc_atomic_disable(struct drm_crtc *crtc,
+                                        struct drm_crtc_state *old_crtc_state)
 {
         struct drm_device *dev = crtc->dev;
         struct fsl_dcu_drm_device *fsl_dev = dev->dev_private;
 
+        /* always disable planes on the CRTC */
+        drm_atomic_helper_disable_planes_on_crtc(old_crtc_state, true);
+
         drm_crtc_vblank_off(crtc);
 
         regmap_update_bits(fsl_dev->regmap, DCU_DCU_MODE,
@@ -127,8 +131,8 @@ static void fsl_dcu_drm_crtc_mode_set_nofb(struct drm_crtc *crtc)
 }
 
 static const struct drm_crtc_helper_funcs fsl_dcu_drm_crtc_helper_funcs = {
+        .atomic_disable = fsl_dcu_drm_crtc_atomic_disable,
         .atomic_flush = fsl_dcu_drm_crtc_atomic_flush,
-        .disable = fsl_dcu_drm_disable_crtc,
         .enable = fsl_dcu_drm_crtc_enable,
         .mode_set_nofb = fsl_dcu_drm_crtc_mode_set_nofb,
 };