linux-kernel - Re: fixed-regulator with enable from another regulator

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Message-ID: <C1E878D9-2C30-454A-AC4D-DB2996313544@dolcini.it>
Date:   Sat, 28 Jan 2023 14:43:23 +0100
From:   Francesco Dolcini <francesco@...cini.it>
To:     Mark Brown <broonie@...nel.org>
CC:     linux-kernel@...r.kernel.org, Liam Girdwood <lgirdwood@...il.com>
Subject: Re: fixed-regulator with enable from another regulator

Il 28 gennaio 2023 14:16:00 CET, Mark Brown <broonie@...nel.org> ha scritto:
>On Fri, Jan 27, 2023 at 10:33:14PM +0100, Francesco Dolcini wrote:
>
>> I am trying to figure out if it is possible with the current
>> regulator-fixed or with any other solution already implemented in Linux
>> to have a regulator enabled from another one.
>
>Not really.  You can model the regulators as sharing the same
>enable if there's a GPIO enable for the parent regulator,
>otherwise it'd need some framework work.

Thanks, I'll propose a patch if needed.

>> I am still not 100% sure if describing this specific hardware connection
>> would be required on my system, maybe I can just ignore all of that.
>
>It seems like a fairly strange hardware design TBH.

Just to shred some light on this weird request, I am not the one who did the design, but there is a reason.

There is one device that requires 3 different voltages, one of those come from a dedicated output of a PMIC, the other 2 from dedicated LDOs.

Having the enable of the 2 LDO on the PMIC output allows to control the power of the device without additional GPIOs usage (that were not available, for instance, while the PMIC can enable/disable the output from I2C).

(not that is relevant for this discussion, but this is of course fine for the power sequencing of this specific device).

Francesco

Hello Mark,