Re: [PATCH] drm: mxsfb: Set proper default bus format when using a bridge

[Marek Vasut]

On 9/28/21 10:55 AM, Guido Günther wrote:
> 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")
>
> Signed-off-by: Guido Günther <agx@xxxxxxxxxxx>
> ---
>
> I'll look at what needs to be done in nwl separately but this also
> unbreaks other bridge seupts that don't to format negotiation yet.
>
>   drivers/gpu/drm/mxsfb/mxsfb_kms.c | 2 ++
>   1 file changed, 2 insertions(+)
>
> diff --git a/drivers/gpu/drm/mxsfb/mxsfb_kms.c b/drivers/gpu/drm/mxsfb/mxsfb_kms.c
> index af6c620adf6e..4ef94cf686b0 100644
> --- a/drivers/gpu/drm/mxsfb/mxsfb_kms.c
> +++ b/drivers/gpu/drm/mxsfb/mxsfb_kms.c
> @@ -369,6 +369,8 @@ 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)
> +			bus_format = MEDIA_BUS_FMT_RGB888_1X24;

Shouldn't the NWL bridge return the correct format ?