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

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Message-ID: <20200213200823.GA28336@kedthinkpad>
Date:   Thu, 13 Feb 2020 22:08:23 +0200
From:   Andrey Lebedev <andrey.lebedev@...il.com>
To:     Maxime Ripard <maxime@...no.tech>
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

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.

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).

[1] excerpt from kernel boot log:

[    4.890975] sun4i-drm display-engine: bound 1e00000.display-frontend (ops sun4i_frontend_driver_exit [sun4i_frontend])
[    4.902032] sun4i-drm display-engine: bound 1e20000.display-frontend (ops sun4i_frontend_driver_exit [sun4i_frontend])
[    4.913467] sun4i-drm display-engine: bound 1e60000.display-backend (ops sun4i_backend_ops [sun4i_backend])
[    4.923806] sun4i-drm display-engine: bound 1e40000.display-backend (ops sun4i_backend_ops [sun4i_backend])
[    4.934451] sun4i-drm display-engine: bound 1c0c000.lcd-controller (ops sun4i_tcon_platform_driver_exit [sun4i_tcon])
[    4.945254] sun4i-tcon 1c0d000.lcd-controller: Missing LVDS properties, Please upgrade your DT
[    4.953935] sun4i-tcon 1c0d000.lcd-controller: LVDS output disabled
[    4.960857] sun4i-drm display-engine: No panel or bridge found... RGB output disabled
[    4.968845] sun4i-drm display-engine: bound 1c0d000.lcd-controller (ops sun4i_tcon_platform_driver_exit [sun4i_tcon])
[    5.080874] sun4i-drm display-engine: bound 1c16000.hdmi (ops sun4i_hdmi_driver_exit [sun4i_drm_hdmi])
[    5.110087] [drm] Initialized sun4i-drm 1.0.0 20150629 for display-engine on minor 0
[    5.763064] sun4i-drm display-engine: fb0: sun4i-drmdrmfb frame buffer device

-- 
Andrey Lebedev aka -.- . -.. -.. . .-.
Software engineer
Homepage: http://lebedev.lt/