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

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Date:   Mon, 4 Oct 2021 10:27:27 +0200
From:   Guido Günther <agx@...xcpu.org>
To:     Lucas Stach <l.stach@...gutronix.de>
Cc:     Andrzej Hajda <a.hajda@...sung.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Robert Foss <robert.foss@...aro.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>, Marek Vasut <marex@...x.de>,
        Stefan Agner <stefan@...er.ch>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        Thierry Reding <thierry.reding@...il.com>,
        Sam Ravnborg <sam@...nborg.org>,
        Ondrej Jirman <megous@...ous.com>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 5/5] drm: mxsfb: Set proper default bus format when
 using a bridge

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@...gutronix.de>
> 
> Regards,
> Lucas
> 
> > Reported-by: Martin Kepplinger <martink@...teo.de>
> > Signed-off-by: Guido Günther <agx@...xcpu.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 */
> 
>