linux-kernel - Re: [PATCH 2/2] ARM: DTS: Add devicetree file for the Galaxy S2

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Date:   Tue, 31 Mar 2020 21:50:19 +0200
From:   Paweł Chmiel <pawel.mikolaj.chmiel@...il.com>
To:     Marek Szyprowski <m.szyprowski@...sung.com>,
        Paul Cercueil <paul@...pouillou.net>
Cc:     Krzysztof Kozlowski <krzk@...nel.org>,
        Kukjin Kim <kgene@...nel.org>,
        Rob Herring <robh+dt@...nel.org>, mark.rutland@....com,
        Stenkin Evgeniy <stenkinevgeniy@...il.com>,
        linux-arm-kernel@...ts.infradead.org,
        linux-samsung-soc@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] ARM: DTS: Add devicetree file for the Galaxy S2

On Tue, 2020-03-31 at 21:29 +0200, Marek Szyprowski wrote:
> Hi
> 
> On 2020-03-31 17:29, Paweł Chmiel wrote:
> > On Tue, 2020-03-31 at 15:55 +0200, Marek Szyprowski wrote:
> > > Hi Paul,
> > > 
> > > On 2020-03-31 15:09, Paul Cercueil wrote:
> > > > Cc: Paweł Chmiel <pawel.mikolaj.chmiel@...il.com>
> > > > 
> > > > Hi Marek,
> > > > 
> > > > Le mar. 31 mars 2020 à 7:36, Marek Szyprowski
> > > > <m.szyprowski@...sung.com> a écrit :
> > > > > Hi Paul,
> > > > > 
> > > > > On 2020-03-18 15:25, Paul Cercueil wrote:
> > > > > > > >    +    };
> > > > > > > >    +
> > > > > > > >    +    tsp_reg: regulator-1 {
> > > > > > > >    +        compatible = "regulator-fixed";
> > > > > > > >    +        regulator-name = "TSP_FIXED_VOLTAGES";
> > > > > > > >    +        regulator-min-microvolt = <3300000>;
> > > > > > > >    +        regulator-max-microvolt = <3300000>;
> > > > > > > >    +        gpio = <&gpl0 3 GPIO_ACTIVE_HIGH>;
> > > > > > > >    +        startup-delay-us = <70000>;
> > > > > > > >    +        enable-active-high;
> > > > > > > >    +        regulator-boot-on;
> > > > > > > >    +        regulator-always-on;
> > > > > > >   always-on and boot-on should not be needed. You have a consumer
> > > > > > > for this
> > > > > > >   regulator.
> > > > > >   About this: the touchscreen driver does not use a regulator, so I
> > > > > >   believe that's why these properties were here.
> > > > > > 
> > > > > >   I sent patches upstream to address the issue:
> > > > > >   https://protect2.fireeye.com/url?k=e8aedc29-b53072b3-e8af5766-0cc47a336fae-759579fd576d8382&u=https://lkml.org/lkml/2020/3/15/94
> > > > > > 
> > > > > > 
> > > > > >   I believe this means I cannot merge the i9100 devicetree until it is
> > > > > >   acked.
> > > > > One more information - similar change has been already posted, but it
> > > > > looks it got lost then: https://patchwork.kernel.org/patch/10550903/
> > > > I was aware of this patch, but didn't know it was sent upstream.
> > > > 
> > > > This other patch uses two regulators, vdd/avdd but doesn't give any
> > > > reason why.
> > > > 
> > > I've checked the UniversalC210 schematic, which uses the same
> > > touchscreen chip. There are 2 supplies to the touchscreen chip: 2.8V VDD
> > > and 3.3V AVDD. Both are enabled by the same GPIO pin though. There is
> > > however no reset GPIO pin there.
> > Hi
> > Don't remember now how it worked on Galaxy S1, but it looks like it has
> > the same setup - two regulators enabled by one GPIO pin.
> 
> It is quite common for the regulators to share the enable GPIO line, so 
> this is not an issue. Regulator framework supports such configuration 
> for ages. I'm curious about the reset GPIO line, which were made 
> mandatory for the regulators control in your patch. I didn't find it on 
> any schematic of the devices with this touch screen, but I don't have a 
> schematic of the Galaxy S1. IMHO the reset signal is simply derived from 
> the supply regulators with some simple circuit, but I don't have 
> schematic of that part.
Hi
Regarding this change - it was suggested during review of v1 version of
those patches. It's first reply here 
https://patchwork.kernel.org/patch/10524007/

> 
> Best regards