[PATCH v2 5/5] drm: mxsfb: Set proper default bus format when using a bridge

[Lucas Stach]

Am Montag, dem 04.10.2021 um 09:27 +0200 schrieb Guido Günther:
> If a bridge doesn't do any bus format handling MEDIA_BUS_FMT_FIXED is
> returned. Fallback to a reasonable default (MEDIA_BUS_FMT_RGB888_1X24) in
> that case.
> 
> This unbreaks e.g. using mxsfb with the nwl bridge and mipi panels.
> 
> Fixes: b776b0f00f24 ("drm: mxsfb: Use bus_format from the nearest bridge if present")
> 
I don't think this qualifies for stable, so I would drop this tag, as
the stable maintainers are quite trigger happy to pull in patches with
a fixes tag. Also the subject isn't quite correct, this isn't setting a
"proper" bus format, but rather adds a fallback. Other than that:

Reviewed-by: Lucas Stach <l.stach at pengutronix.de>

Regards,
Lucas

> Reported-by: Martin Kepplinger <martink at posteo.de>
> Signed-off-by: Guido Günther <agx at sigxcpu.org>

> ---
>  drivers/gpu/drm/mxsfb/mxsfb_kms.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/gpu/drm/mxsfb/mxsfb_kms.c b/drivers/gpu/drm/mxsfb/mxsfb_kms.c
> index d6abd2077114..e3fbb8b58d5d 100644
> --- a/drivers/gpu/drm/mxsfb/mxsfb_kms.c
> +++ b/drivers/gpu/drm/mxsfb/mxsfb_kms.c
> @@ -369,6 +369,12 @@ static void mxsfb_crtc_atomic_enable(struct drm_crtc *crtc,
>  			drm_atomic_get_new_bridge_state(state,
>  							mxsfb->bridge);
>  		bus_format = bridge_state->input_bus_cfg.format;
> +		if (bus_format == MEDIA_BUS_FMT_FIXED) {
> +			dev_warn_once(drm->dev,
> +				      "Bridge does not provide bus format, assuming MEDIA_BUS_FMT_RGB888_1X24.\n"
> +				      "Please fix bridge driver by handling atomic_get_input_bus_fmts.\n");
> +			bus_format = MEDIA_BUS_FMT_RGB888_1X24;
> +		}
>  	}
>  
>  	/* If there is no bridge, use bus format from connector */