[PATCH] drm: mxsfb: check framebuffer pitch

[Stefan Agner]

The lcdif IP does not support a framebuffer pitch (stride) other than
the CRTC width. Check for equality and reject the state otherwise.

This prevents a distorted picture when using 640x800 and running the
Mesa graphics stack. Mesa tires to use a cache aligned stride, which
leads at that particular resolution to width != stride. Currently
Mesa has no fallback behavior, but rejecting this configuration allows
userspace to handle the issue correctly.

Signed-off-by: Stefan Agner <ste...@agner.ch>
---
 drivers/gpu/drm/mxsfb/mxsfb_kms.c | 22 ++++++++++++++++++----
 1 file changed, 18 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/mxsfb/mxsfb_kms.c 
b/drivers/gpu/drm/mxsfb/mxsfb_kms.c
index b721b8b262ce..79aa14027f91 100644
--- a/drivers/gpu/drm/mxsfb/mxsfb_kms.c
+++ b/drivers/gpu/drm/mxsfb/mxsfb_kms.c
@@ -403,14 +403,28 @@ static int mxsfb_plane_atomic_check(struct drm_plane 
*plane,
 {
        struct mxsfb_drm_private *mxsfb = to_mxsfb_drm_private(plane->dev);
        struct drm_crtc_state *crtc_state;
+       unsigned int pitch;
+       int ret;
 
        crtc_state = drm_atomic_get_new_crtc_state(plane_state->state,
                                                   &mxsfb->crtc);
 
-       return drm_atomic_helper_check_plane_state(plane_state, crtc_state,
-                                                  DRM_PLANE_HELPER_NO_SCALING,
-                                                  DRM_PLANE_HELPER_NO_SCALING,
-                                                  false, true);
+       ret = drm_atomic_helper_check_plane_state(plane_state, crtc_state,
+                                                 DRM_PLANE_HELPER_NO_SCALING,
+                                                 DRM_PLANE_HELPER_NO_SCALING,
+                                                 false, true);
+       if (ret || !plane_state->visible)
+               return ret;
+
+       pitch = crtc_state->mode.hdisplay *
+               plane_state->fb->format->cpp[0];
+       if (plane_state->fb->pitches[0] != pitch) {
+               dev_err(plane->dev->dev,
+                       "Invalid pitch: fb and crtc widths must be the same");
+               return -EINVAL;
+       }
+
+       return 0;
 }
 
 static void mxsfb_plane_primary_atomic_update(struct drm_plane *plane,
-- 
2.28.0