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SubjectRe: [PATCH v2 1/2] pinctrl: Allow a device to indicate when to force a state
* Florian Fainelli <f.fainelli@gmail.com> [171129 18:17]:
> On 11/29/2017 09:45 AM, Tony Lindgren wrote:
> > * Florian Fainelli <f.fainelli@gmail.com> [171129 17:37]:
> >> On 11/29/2017 09:01 AM, Tony Lindgren wrote:
> >>> * Florian Fainelli <f.fainelli@gmail.com> [171102 23:18]:
> >>>> It may happen that a device needs to force applying a state, e.g:
> >>>> because it only defines one state of pin states (default) but loses
> >>>> power/register contents when entering low power modes. Add a
> >>>> pinctrl_dev::flags bitmask to help describe future quirks and define
> >>>> PINCTRL_FLG_FORCE_STATE as such a settable flag.
> >>>
> >>> It makes sense to tag the existing state with the context loss
> >>> information as otherwise we'll be duplicating the state in the
> >>> pinctrl driver potentially for hundreds of pins.
> >>>
> >>> Maybe this patch description should clarify that it's the
> >>> pinctrl device restoring the pin state, not the pinctrl
> >>> consumer devices?
> >>>
> >>> So maybe just "a pinctrl device needs to force apply a state"
> >>> instead of just device above?
> >>
> >> It's a bit more involved than that, the pinctrl consumer device might
> >> want to restore a particular state by calling pinctrl_select_state(),
> >> however, because of the (p->state == state)check, the pinctrl provider
> >> driver has no chance of making that call do the actual HW programming.
> >
> > Hmm but isn't it the pinctrl provider device losing context here?
>
> It is the pinctrl provider indeed.
>
> > I think the restore of the pin state should somehow happen automatically
> > by the pinctrl provider driver without a need for the pinctrl consumer
> > drivers to do anything.
>
> Correct.

OK thanks for confirming that.

> > Or what's the use case for pinctrl consumer driver wanting to store
> > a pin?
>
> I actually meant that a consumer driver could aalso call
> pinctrl_select_state() in one of its resume callback for instance, but
> if the pinctrl provider driver does nothing (or rather the core, on
> behalf of the provider), this would be an issue. This was not super
> clear, so I will stop using that example from now on :)

OK yeah that's probably where the confusion comes from :)

Tony

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