linux-kernel - Re: [PATCH 1/2] regulator: core: Add coupled regulators mechanism

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Message-ID: <20170919144738.g2xwjaph6bjvwt35@sirena.co.uk>
Date:   Tue, 19 Sep 2017 15:47:38 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Maciej Purski <m.purski@...sung.com>
Cc:     linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        Liam Girdwood <lgirdwood@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Subject: Re: [PATCH 1/2] regulator: core: Add coupled regulators mechanism

On Tue, Sep 19, 2017 at 04:35:54PM +0200, Maciej Purski wrote:

Please fix your mail client to word wrap within paragraphs at something
substantially less than 80 columns.  Doing this makes your messages much
easier to read and reply to.

> On 09/19/2017 03:09 PM, Mark Brown wrote:

> and from my new function regulator_set_coupled_voltage(). I added this in order to avoid
> code duplication. I agree that the name might not be adequate. What name would you find more suitable?

I think if the single regulator case isn't just a special case of the
multi regulator case then we're doing this wrong and there will be
maintainability problems so I'm not sure if this split makes sense at
all.

> > There's no locking here, and we appear to take no action when these
> > counts change - do we need to bother with this at all?

> Variable enable_count is used for checking if both regulators are enabled and there's a need for
> using the coupling mechanism. It is checked in regulator_set_coupled_voltage_unlocked(), where the
> mutex is already locked. I think that locking it here would be useful. Thanks.

So what happens if one regulator is enabled after the other and the
constraints become unsatisified?

> > > +	/* Get voltages desired by all consumers of the coupled regulator */
> > > +	for (i = 0; i < 2; i++) {

> > It appears we can't couple more than two regulators?

> We can couple just two regulators. We have never found any case for coupling
> more than two regulators. Limiting the mechanism to just two regulators simplifies
> algorithm a little bit. Would you prefer it working for more than two
> regulators also even if there isn't any use case?

It seems cleaner.

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