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

[Stefan Eichenberger <eichest@gmail.com>]

Hi Krzysztof and Linux,

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@gmail.com> wrote:
> 
> > From: Stefan Eichenberger <stefan.eichenberger@toradex.com>
> >
> > Add a new property to indicate that the device should be powered off in
> > suspend mode.
> >
> > Signed-off-by: Stefan Eichenberger <stefan.eichenberger@toradex.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.
> 
> I can't help but wonder: shouldn't that pretty much be the default behaviour
> if wakeup-source is *not* specified?
> 
> I.e. the property kind of describes !wakeup-source.

The maxtouch controller has a deep sleep mode which is currently used
without powering down vdd and vdda. However, because we have a shared
regulator which powers other peripherals that we want to shut down in
suspend we need a way to power down vdd and vdda. However, I agree this
is not really a feature of the device. The feature would basically be
the internal deep sleep mode. I didn't want to change the default
behaviour of the driver, so I added this property but maybe I could
change it to:

atmel,deep-sleep:
  description: |
     Use the maxtouch deep-sleep mode instead of powering down vdd and
     vdda.

Or to not change the default behaviour:
atmel,no-deep-sleep:
  description: |
     Do not use the maxtouch deep-sleep mode but power down vdd and vdda
     in suspend.

As I understand the datasheet even if the maxtouch is using its deep
sleep mode it does not act as a wakeup source. It is just faster in
waking up because it can keep the configuration in memory.

Regards,
Stefan