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

[Guido Günther]

Hi,
On Mon, Oct 04, 2021 at 09:58:37AM +0200, Lucas Stach wrote:
> 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:

Adjusted for v3 (which I'll hold off a bit in case there are more
comments) and dropped the Fixes: tag which is on the nwl driver
only now. thanks!
 -- Guido

> 
> Reviewed-by: Lucas Stach <l.stach@xxxxxxxxxxxxxx>
> 
> Regards,
> Lucas
> 
> > Reported-by: Martin Kepplinger <martink@xxxxxxxxx>
> > Signed-off-by: Guido Günther <agx@xxxxxxxxxxx>
> 
> > ---
> >  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 */
> 
>