linux-kernel - Re: [PATCH v2 1/2] pinctrl: Allow a device to indicate when to force a state

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Date:   Wed, 29 Nov 2017 09:35:14 -0800
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Tony Lindgren <tony@...mide.com>
Cc:     linux-gpio@...r.kernel.org,
        Linus Walleij <linus.walleij@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        ckeepax@...nsource.cirrus.com, ckeepax@...nsource.wolfsonmicro.com,
        swarren@...dia.com, andy.shevchenko@...il.com, alcooperx@...il.com,
        bcm-kernel-feedback-list@...adcom.com
Subject: Re: [PATCH v2 1/2] pinctrl: Allow a device to indicate when to force
 a state

On 11/29/2017 09:01 AM, Tony Lindgren wrote:
> * Florian Fainelli <f.fainelli@...il.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.
-- 
Florian