Re: [PATCH] drm: rcar-du: Don't create encoder for unconnected LVDS outputs

From: Geert Uytterhoeven <geert@linux-m68k.org>
To: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: DRI Development <dri-devel@lists.freedesktop.org>,
	Linux-Renesas <linux-renesas-soc@vger.kernel.org>,
	Kieran Bingham <kieran.bingham@ideasonboard.com>
Subject: Re: [PATCH] drm: rcar-du: Don't create encoder for unconnected LVDS outputs
Date: Tue, 28 Sep 2021 10:55:57 +0200	[thread overview]
Message-ID: <CAMuHMdW6Y4rhcH4EfjnzkPvWhm2ok=7E_3Cswe=5bnozGzpmGA@mail.gmail.com> (raw)
In-Reply-To: <YSO2h40mJN17FGvd@pendragon.ideasonboard.com>

Hi Laurent,

On Mon, Aug 23, 2021 at 4:54 PM Laurent Pinchart
<laurent.pinchart@ideasonboard.com> wrote:
> On Mon, Aug 23, 2021 at 02:25:32PM +0200, Geert Uytterhoeven wrote:
> > On Sun, Aug 22, 2021 at 2:36 AM Laurent Pinchart wrote:
> > > On R-Car D3 and E3, the LVDS encoders provide the pixel clock to the DU,
> > > even when LVDS outputs are not used. For this reason, the rcar-lvds
> > > driver probes successfully on those platforms even if no further bridge
> > > or panel is connected to the LVDS output, in order to provide the
> > > rcar_lvds_clk_enable() and rcar_lvds_clk_disable() functions to the DU
> > > driver.
> > >
> > > If an LVDS output isn't connected, trying to create a DRM connector for
> > > the output will fail. Fix this by skipping connector creation in that
> > > case, and also skip creation of the DRM encoder as there's no point in
> > > an encoder without a connector.
> > >
> > > Fixes: e9e056949c92 ("drm: rcar-du: lvds: Convert to DRM panel bridge helper")
> > > Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
> >
> > Can you please change that to
> > Reported-by: Geert Uytterhoeven <geert+renesas@glider.be>
> > ?
>
> Sure thing.

Thanks!

> > > Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
> >
> > Thanks, the scary warning on Ebisu-4D is gone, so
> > Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
> >
> > Disclaimer: there are no displays connected to my Ebisu-4D.
>
> That's the best way to ensure the absence of display issues. It works
> great for camera testing too, if you also remove networking and storage
> :-)

Any chance this fix can make it upstream?
The fix was created before the issue entered upstream in v5.15-rc1.

Thanks!

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds