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

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Date:   Wed, 1 Apr 2020 12:42:14 +0200
From:   Marek Szyprowski <m.szyprowski@...sung.com>
To:     Paweł Chmiel <pawel.mikolaj.chmiel@...il.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

Hi Paweł,

On 2020-03-31 21:50, Paweł Chmiel wrote:
> On Tue, 2020-03-31 at 21:29 +0200, Marek Szyprowski wrote:
>> On 2020-03-31 17:29, Paweł Chmiel wrote:
>>> On Tue, 2020-03-31 at 15:55 +0200, Marek Szyprowski wrote:
>>>> On 2020-03-31 15:09, Paul Cercueil wrote:
>>>>> Le mar. 31 mars 2020 à 7:36, Marek Szyprowski
>>>>> <m.szyprowski@...sung.com> a écrit :
>>>>>> 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/

Well, I know that this has been requested in v1 review, but I thought 
that you have tested v3 of your patch on I9000, thus I was curious about 
that reset GPIO line.

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland