Re: [PATCH] drm: renesas: shmobile: Add drm_panic support

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Geert,

Thank you for the patch.

On Mon, May 27, 2024 at 03:34:48PM +0200, Geert Uytterhoeven wrote:
> Add support for the drm_panic module, which displays a message on
> the screen when a kernel panic occurs.
> 
> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
> ---
> Tested on Armadillo-800-EVA.
> ---
>  drivers/gpu/drm/renesas/shmobile/shmob_drm_plane.c | 14 +++++++++++++-
>  1 file changed, 13 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/renesas/shmobile/shmob_drm_plane.c b/drivers/gpu/drm/renesas/shmobile/shmob_drm_plane.c
> index 07ad17d24294d5e6..9d166ab2af8bd231 100644
> --- a/drivers/gpu/drm/renesas/shmobile/shmob_drm_plane.c
> +++ b/drivers/gpu/drm/renesas/shmobile/shmob_drm_plane.c
> @@ -273,6 +273,13 @@ static const struct drm_plane_helper_funcs shmob_drm_plane_helper_funcs = {
>  	.atomic_disable = shmob_drm_plane_atomic_disable,
>  };
>  
> +static const struct drm_plane_helper_funcs shmob_drm_primary_plane_helper_funcs = {
> +	.atomic_check = shmob_drm_plane_atomic_check,
> +	.atomic_update = shmob_drm_plane_atomic_update,
> +	.atomic_disable = shmob_drm_plane_atomic_disable,
> +	.get_scanout_buffer = drm_fb_dma_get_scanout_buffer,
> +};
> +
>  static const struct drm_plane_funcs shmob_drm_plane_funcs = {
>  	.update_plane = drm_atomic_helper_update_plane,
>  	.disable_plane = drm_atomic_helper_disable_plane,
> @@ -310,7 +317,12 @@ struct drm_plane *shmob_drm_plane_create(struct shmob_drm_device *sdev,
>  
>  	splane->index = index;
>  
> -	drm_plane_helper_add(&splane->base, &shmob_drm_plane_helper_funcs);
> +	if (type == DRM_PLANE_TYPE_PRIMARY)
> +		drm_plane_helper_add(&splane->base,
> +				     &shmob_drm_primary_plane_helper_funcs);
> +	else
> +		drm_plane_helper_add(&splane->base,
> +				     &shmob_drm_plane_helper_funcs);

It's not very nice to have to provide different operations for the
primary and overlay planes. The documentation of
drm_fb_dma_get_scanout_buffer() states

 * @plane: DRM primary plane

If the intent is that only primary planes will be used to display the
panic message, shouldn't drm_panic_register() skip overlay planes ? It
would simplify drivers.

>  
>  	return &splane->base;
>  }

-- 
Regards,

Laurent Pinchart