linux-kernel - Re: [PATCH v1 1/2] dt-bindings: input: atmel,maxtouch: add poweroff-in-suspend property

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Message-ID: <ZXOoy8mFdhUQsZAu@google.com>
Date:   Fri, 8 Dec 2023 23:37:47 +0000
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     Linus Walleij <linus.walleij@...aro.org>
Cc:     Stefan Eichenberger <eichest@...il.com>, nick@...anahar.org,
        robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
        conor+dt@...nel.org, nicolas.ferre@...rochip.com,
        alexandre.belloni@...tlin.com, claudiu.beznea@...on.dev,
        linux-input@...r.kernel.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Stefan Eichenberger <stefan.eichenberger@...adex.com>
Subject: Re: [PATCH v1 1/2] dt-bindings: input: atmel,maxtouch: add
 poweroff-in-suspend property

Hi Linus, Krzysztof,

On Fri, Dec 08, 2023 at 01:54:21PM +0100, Linus Walleij wrote:
> On Thu, Dec 7, 2023 at 12:13 PM Stefan Eichenberger <eichest@...il.com> wrote:
> 
> > From: Stefan Eichenberger <stefan.eichenberger@...adex.com>
> >
> > Add a new property to indicate that the device should be powered off in
> > suspend mode.
> >
> > Signed-off-by: Stefan Eichenberger <stefan.eichenberger@...adex.com>
> (...)
> > +  atmel,poweroff-in-suspend:
> > +    description: |
> > +      When this property is set, all supplies are turned off when the system is
> > +      going to suspend.
> > +    type: boolean
>    wakeup-source:
>      type: boolean
> 
> As Krzysztof says it seems you are describing an operating system feature.

It appears to be an OS feature, but I would argue that it is also a
property of a board. It is tempting to say that if DTS defines supplies
for the controller we should use them to power off the controller in
suspend, otherwise we should use the deep sleep functionality of the
controller. But a mere presence of regulators does not indicate if they
can actually be powered off in suspend (i.e. if controllers shares power
rails with another device that can be a wakeup source), so we need to
have additional hints on how OS should behave on a given device.

On top of that we have regulator framework supplying dummy regulators...

Thanks.

-- 
Dmitry