[alsa-devel] Is that reasonable to support pinctrl PM in ASoC core?

[Mark Brown]

On Thu, Oct 24, 2013 at 03:19:03PM +0200, Linus Walleij wrote:

> This makes a lot of sense, the only problem I have traditionally had
> with this is that there exist cases where you want to put pinctrl
> handles to sleep or idle aside from runtime PM.

Yeah, that was my concern.

> - I2C or SPI hosts with no devices connected to them should be
>   nailed to sleep. (It's not possible to detect an unused I2C or SPI
>   host today, but a feature we should add.)

The SPI case should be mostly handled already if this is integrated via
runtime PM - we have core support for idling controllers whenever there
is no transfer active.  That should go off for devices that aren't
connected to anything.

I should probably go and implement an I2C version of that.

> Maybe the right way to do these is also to use runtime_pm*,
> but the thing is that today these things are done also when
> CONFIG_PM_RUNTIME is not set. Which is something you
> might sometimes want.

> Or not? Should we say that unless you have
> CONFIG_PM_RUNTIME you don't deserve saving these
> microamps anyway?

Personally I tend to think that people who care probably ought to be
using runtime PM but that's not a sufficiently general view to insist
on.

As we discussed in person earlier how about we merge this on a subsystem
basis and then once we've established what the pattern really is we
think about putting it into the core.  Nicolin, do you want to write a
patch for this?
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