linux-kernel - Re: [PATCH 1/4] ARM: dts: omap3-n900: fix LCD reset line polarity

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Date:   Tue, 11 Oct 2022 14:37:26 +0200
From:   Sebastian Reichel <sre@...nel.org>
To:     Tony Lindgren <tony@...mide.com>
Cc:     Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Benoît Cousson <bcousson@...libre.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Rob Herring <robh+dt@...nel.org>, devicetree@...r.kernel.org,
        linux-omap@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] ARM: dts: omap3-n900: fix LCD reset line polarity

Hi,

On Tue, Oct 11, 2022 at 08:45:54AM +0300, Tony Lindgren wrote:
> * Dmitry Torokhov <dmitry.torokhov@...il.com> [221004 21:26]:
> > The LCD driver (panel-sony-acx565akm), when probing, starts with line
> > driven low, and then toggles it to high and keeps it there. Also, the
> > line is driven low when powering off the device, and ls released when
> > powering it back on. This means that the reset line should be described
> > as "active low" in DTS. This will be important when the driver is
> > converted to gpiod API which respects the polarity declared in DTS.
> 
> We should ensure these patches get merged together with the driver
> change to avoid breaking LCD for booting. Probably no need to have
> the driver quirk handling for inverted polartity in this case.
> 
> It's probably easiest to have an immutable branch for the driver
> changes I can base the dts changes on. Or I can ack the dts changes
> if they get merged with the driver.

Both drivers are already using gpiod API:

drivers/gpu/drm/panel/panel-sony-acx565akm.c
drivers/gpu/drm/panel/panel-dsi-cm.c

So this just breaks things.

-- Sebastian

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