Hi Liu Ying. On Mon, Jun 12, 2023 at 03:55:30PM +0800, Liu Ying wrote: > When disabling overlay plane in mxsfb_plane_overlay_atomic_update(), > overlay plane's framebuffer pointer is NULL. So, dereferencing it would > cause a kernel Oops(NULL pointer dereferencing). Fix the issue by > disabling overlay plane in mxsfb_plane_overlay_atomic_disable() instead. Reading the above I had expected that some code was dropped from mxsfb_plane_overlay_atomic_update(). I do not know the driver code, but was confused so decided to give feedback. Sam > > Fixes: cb285a5348e7 ("drm: mxsfb: Replace mxsfb_get_fb_paddr() with drm_fb_cma_get_gem_addr()") > Signed-off-by: Liu Ying <victor.liu@xxxxxxx> > --- > drivers/gpu/drm/mxsfb/mxsfb_kms.c | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/drivers/gpu/drm/mxsfb/mxsfb_kms.c b/drivers/gpu/drm/mxsfb/mxsfb_kms.c > index 3bcc9c0f2019..7ed2516b6de0 100644 > --- a/drivers/gpu/drm/mxsfb/mxsfb_kms.c > +++ b/drivers/gpu/drm/mxsfb/mxsfb_kms.c > @@ -611,6 +611,14 @@ static void mxsfb_plane_overlay_atomic_update(struct drm_plane *plane, > writel(ctrl, mxsfb->base + LCDC_AS_CTRL); > } > > +static void mxsfb_plane_overlay_atomic_disable(struct drm_plane *plane, > + struct drm_atomic_state *state) > +{ > + struct mxsfb_drm_private *mxsfb = to_mxsfb_drm_private(plane->dev); > + > + writel(0, mxsfb->base + LCDC_AS_CTRL); > +} > + > static bool mxsfb_format_mod_supported(struct drm_plane *plane, > uint32_t format, > uint64_t modifier) > @@ -626,6 +634,7 @@ static const struct drm_plane_helper_funcs mxsfb_plane_primary_helper_funcs = { > static const struct drm_plane_helper_funcs mxsfb_plane_overlay_helper_funcs = { > .atomic_check = mxsfb_plane_atomic_check, > .atomic_update = mxsfb_plane_overlay_atomic_update, > + .atomic_disable = mxsfb_plane_overlay_atomic_disable, > }; > > static const struct drm_plane_funcs mxsfb_plane_funcs = { > -- > 2.37.1