linux-kernel - Re: [PATCH] ARM: dts: turris-omnia: Add mcu node

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Message-ID: <20220903152735.2ga3iwrivh6zhibf@pali>
Date:   Sat, 3 Sep 2022 17:27:35 +0200
From:   Pali Rohár <pali@...nel.org>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Gregory Clement <gregory.clement@...tlin.com>,
        Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Marek Behun <marek.behun@....cz>,
        linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ARM: dts: turris-omnia: Add mcu node

On Friday 02 September 2022 00:45:58 Andrew Lunn wrote:
> On Wed, Aug 31, 2022 at 04:28:09PM +0200, Pali Rohár wrote:
> > PING?
> > 
> > On Friday 19 August 2022 15:11:52 Pali Rohár wrote:
> > > At i2c address 0x2a is MCU command interface which provides access to GPIOs
> > > connected to Turris Omnia MCU. So define mcu node in Turris Omnia DTS file.
> > > 
> > > Signed-off-by: Pali Rohár <pali@...nel.org>
> > > 
> > > ---
> > > Same change was already sent to U-Boot project together with driver. As
> > > Turris Omnia DTS file is shared between Linux kernel U-Boot, I'm sending
> > > this change also in Linux. There is a plan to write also Linux driver for
> > > Turris Omnia MCU, like there is already in U-Boot.
> > > 
> > > https://source.denx.de/u-boot/u-boot/-/commit/832738974806e6264a3d0ac2aaa92d0f662fd128
> > > https://source.denx.de/u-boot/u-boot/-/blob/master/drivers/gpio/turris_omnia_mcu.c
> > > ---
> > >  arch/arm/boot/dts/armada-385-turris-omnia.dts | 8 +++++++-
> > >  1 file changed, 7 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/arch/arm/boot/dts/armada-385-turris-omnia.dts b/arch/arm/boot/dts/armada-385-turris-omnia.dts
> > > index f4878df39753..f655e9229d68 100644
> > > --- a/arch/arm/boot/dts/armada-385-turris-omnia.dts
> > > +++ b/arch/arm/boot/dts/armada-385-turris-omnia.dts
> > > @@ -184,7 +184,13 @@
> > >  			#size-cells = <0>;
> > >  			reg = <0>;
> > >  
> > > -			/* STM32F0 command interface at address 0x2a */
> > > +			/* MCU command i2c API */
> > > +			mcu: mcu@2a {
> > > +				compatible = "cznic,turris-omnia-mcu";
> > > +				reg = <0x2a>;
> > > +				gpio-controller;
> > > +				#gpio-cells = <3>;
> > > +			};
> 
> Please document the binding, preferably in yaml.

I'm not going to send any new yaml dt binding document as I see that
dt bindings is clearly deprecated project. Either patches for dt
bindings are waiting without any answer for months (maybe year?) or
patches are ignored/not accepted by beyond reasons or there are request
for changes which cannot work on the real hardware or that new yaml
cannot be parsed/validated due to ton of bugs in other schemas.

Sorry, this is just a waste of time and energy to write new those yamls
as it does not bring any value.

> I'm also not sure what the DT people will say about the node name mcu.
> I don't see any examples of that in the binding documentation. They
> might request you rename it to gpio-controller, unless it does more
> than GPIO? And if it does do more than GPIO we are then into mfd
> territory, and the binding then becomes much more interesting. Then we
> start the questions, are you defining a ABI now, before there is even
> a driver for it?
> 
>        Andrew

Yes, there is already driver. See my previous email, I mentioned it and
also I wrote link for this driver. Moreover now driver is merged in
upstream u-boot.

Driver has currently implemented only GPIO support, but other functions
supported by MCU would be implemented later.