linux-kernel - Re: [PATCH v7] regulator: fixed: Convert to use GPIO descriptor only

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Date:   Fri, 12 Oct 2018 11:39:15 +0100
From:   Jon Hunter <jonathanh@...dia.com>
To:     Marcel Ziswiler <marcel.ziswiler@...adex.com>,
        "linus.walleij@...aro.org" <linus.walleij@...aro.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "robert.jarzmik@...e.fr" <robert.jarzmik@...e.fr>,
        "aaro.koskinen@....fi" <aaro.koskinen@....fi>,
        "jacopo@...ndi.org" <jacopo@...ndi.org>,
        "m.szyprowski@...sung.com" <m.szyprowski@...sung.com>,
        "rmk+kernel@...linux.org.uk" <rmk+kernel@...linux.org.uk>,
        "broonie@...nel.org" <broonie@...nel.org>,
        "shc_work@...l.ru" <shc_work@...l.ru>,
        "haojian.zhuang@...il.com" <haojian.zhuang@...il.com>,
        "lgirdwood@...il.com" <lgirdwood@...il.com>,
        "rppt@...ux.vnet.ibm.com" <rppt@...ux.vnet.ibm.com>,
        "zonque@...il.com" <zonque@...il.com>,
        "marc.zyngier@....com" <marc.zyngier@....com>,
        "philipp.zabel@...il.com" <philipp.zabel@...il.com>,
        "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
        "jmkrzyszt@...il.com" <jmkrzyszt@...il.com>,
        "geert+renesas@...der.be" <geert+renesas@...der.be>
Subject: Re: [PATCH v7] regulator: fixed: Convert to use GPIO descriptor only


On 12/10/18 10:43, Marcel Ziswiler wrote:
> On Thu, 2018-10-11 at 19:47 +0200, Linus Walleij wrote:
>> On Thu, Oct 11, 2018 at 5:34 PM Marcel Ziswiler
>> <marcel.ziswiler@...adex.com> wrote:
>>
>>> I guess that is also what broke HDMI on Apalis/Colibri T30 causing
>>> me
>>> to submit a fix [1]. I may also help testing.
>>
>> I see there are many ways to skin this cat.
> 
> Yes, as a matter of fact I screened the kernel concerning this multi
> gpio stuff but could not quite find many examples and no mentioning
> anywhere whether or not this is actually allowed. So I kind of assumed
> that this may just not really be allowed and cooked up my patch which
> is anyway kind of a cleaner solution. I mean explicitly modelling the
> GPIO into some intermediate regulator supplying the others.

See the function 'regulator_ena_gpio_request()', it states that the same
GPIO pin can be shared among regulators.

We had the same situation for Tegra124 Jetson TK1 but I don't think that
adding a pseudo intermediate regulator is cleaner. If the GPIO controls
more than one regulator, I don't see why is it necessary to change the
DT. There are several other people reporting the same problem with
various different boards. So this does seem to be a common usage.

Cheers
Jon

-- 
nvpublic