linux-kernel - Re: [PATCH v2 2/2] ARM: sun7i: dts: Add LVDS panel support on A20

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Message-ID: <20200214075218.huxdhmd4qfoakat2@gilmour.lan>
Date:   Fri, 14 Feb 2020 08:52:18 +0100
From:   Maxime Ripard <maxime@...no.tech>
To:     Andrey Lebedev <andrey.lebedev@...il.com>
Cc:     wens@...e.org, airlied@...ux.ie, daniel@...ll.ch,
        dri-devel@...ts.freedesktop.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-sunxi@...glegroups.com, Andrey Lebedev <andrey@...edev.lt>
Subject: Re: [PATCH v2 2/2] ARM: sun7i: dts: Add LVDS panel support on A20

Hi,

On Thu, Feb 13, 2020 at 10:08:23PM +0200, Andrey Lebedev wrote:
> On Thu, Feb 13, 2020 at 10:43:04AM +0100, Maxime Ripard wrote:
> > On Thu, Feb 13, 2020 at 12:23:57AM +0200, andrey.lebedev@...il.com wrote:
> > > From: Andrey Lebedev <andrey@...edev.lt>
> > >
> > > Define pins for LVDS channels 0 and 1, configure reset line for tcon0 and
> > > provide sample LVDS panel, connected to tcon0.
> > >
> > > Signed-off-by: Andrey Lebedev <andrey@...edev.lt>
> >
> > And this prefix should be ARM: dts: sun7i ;)
>
> Ah, thanks, I think I've got the pattern now!
>
> > > +			/omit-if-no-ref/
> > > +			lcd_lvds0_pins: lcd_lvds0_pins {
> >
> > underscores in the node names will create a dtc warning at
> > compilation, you should use lcd-lvds0-pins instead.

It's silenced by default, but you'll get them with W=1

> You're right, I wasn't following the naming convention here. dtc doesn't
> produce any warning on this though. Fixed that anyway.
>
> > This will create a spurious warning message for TCON1, since we
> > adjusted the driver to tell it supports LVDS, but there's no LVDS
> > reset line, so we need to make it finer grained.
>
> Yes, I can attribute two of the messages in my dmesg log [1] to this
> ("Missing LVDS properties" and "LVDS output disabled". "sun4i-tcon
> 1c0d000.lcd-controller" is indeed tcon1). And yes, I can see how they
> can be confusing to someone.
>
> I'd need some pointers on how to deal with that though (if we want to do
> it in this scope).

Like I was mentionning, you could introduce a new compatible for each
TCON (tcon0 and tcon1) and only set the support_lvds flag for tcon0

Maxime

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