linux-kernel - Re: [PATCH RFC] regulator: core: fix handling negative voltages e.g. in EPD PMICs

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Date:   Mon, 24 Feb 2020 19:46:25 +0100
From:   Andreas Kemnade <andreas@...nade.info>
To:     Mark Brown <broonie@...nel.org>
Cc:     hns@...delico.com, j.neuschaefer@....net, contact@...lk.fr,
        GNUtoo@...erdimension.org, josua.mayer@....eu, lgirdwood@...il.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC] regulator: core: fix handling negative voltages
 e.g. in EPD PMICs

Hi,

On Mon, 24 Feb 2020 12:05:12 +0000
Mark Brown <broonie@...nel.org> wrote:

> On Sun, Feb 23, 2020 at 04:35:01PM +0100, Andreas Kemnade wrote:
> 
> > An alternative would be to handle voltages as absolute values.
> > There are probably no regulators with support both negative
> > and positive output.  
> 
> This is what'd be needed, your approach here is a bit of a hack and
> leaves some values unrepresentable if they overlap with errnos which
> obviously has issues if someone has a need for those values.  Ground is
> to a large extent somewhat arbatrary anyway and some systems do just
> redefine it as part of their normal operation (eg, VMID based audio
> systems) so this wouldn't be a huge departure.

Thanks for clarification, outputs from 0mV to -4mV would not be be
representable. I am now converting stuff to think positive ;-) That
is good to decide early before pushing my huge pile of things needed
for EPD support on top of mainline somewhere.
Parallel I am evaluating upstreaming of the tps65181 driver which
probably ends up in a rewrite...

Regards,
Andreas

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