From: Tony Lindgren <tony@atomide.com>
To: Florian Fainelli <f.fainelli@gmail.com>
Cc: linux-gpio@vger.kernel.org,
Linus Walleij <linus.walleij@linaro.org>,
Rob Herring <robh+dt@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS"
<devicetree@vger.kernel.org>,
open list <linux-kernel@vger.kernel.org>,
ckeepax@opensource.cirrus.com,
ckeepax@opensource.wolfsonmicro.com, swarren@nvidia.com,
andy.shevchenko@gmail.com, alcooperx@gmail.com,
bcm-kernel-feedback-list@broadcom.com
Subject: Re: [PATCH v2 1/2] pinctrl: Allow a device to indicate when to force a state
Date: Wed, 29 Nov 2017 10:27:29 -0800 [thread overview]
Message-ID: <20171129182729.GK28152@atomide.com> (raw)
In-Reply-To: <ff2e6268-4738-4858-5cf0-368a23c81ccc@gmail.com>
* 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
next prev parent reply other threads:[~2017-11-29 18:27 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-02 23:15 [PATCH v2 0/2] pinctrl: Allow indicating loss of state across suspend/resume Florian Fainelli
2017-11-02 23:15 ` [PATCH v2 1/2] pinctrl: Allow a device to indicate when to force a state Florian Fainelli
[not found] ` <20171102231551.16220-2-f.fainelli-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2017-11-29 13:06 ` Linus Walleij
2017-11-29 17:01 ` Tony Lindgren
2017-11-29 17:35 ` Florian Fainelli
2017-11-29 17:45 ` Tony Lindgren
2017-11-29 18:15 ` Florian Fainelli
2017-11-29 18:27 ` Tony Lindgren [this message]
2017-11-02 23:15 ` [PATCH v2 2/2] pinctrl: Allow indicating loss of pin states during low-power Florian Fainelli
2017-11-29 13:01 ` Linus Walleij
[not found] ` <CACRpkdZtFRB_iy1bDPZ0wkK0jf7pkTGtbZG4gQUJVR+eiO+dhA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-11-29 17:02 ` Tony Lindgren
[not found] ` <20171129170247.GI28152-4v6yS6AI5VpBDgjK7y7TUQ@public.gmane.org>
2017-11-29 17:37 ` Florian Fainelli
[not found] ` <96cf5d74-3acf-07b9-9ad8-1011cd99a860-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2017-12-02 12:48 ` Linus Walleij
2017-12-10 23:38 ` Florian Fainelli
[not found] ` <908c66f9-f9bd-a4df-e241-75595a3a3e27-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2017-12-20 7:24 ` Linus Walleij
2017-12-30 19:31 ` Florian Fainelli
[not found] ` <20171102231551.16220-1-f.fainelli-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2017-11-03 10:37 ` [PATCH v2 0/2] pinctrl: Allow indicating loss of state across suspend/resume Charles Keepax
2017-11-03 16:11 ` Tony Lindgren
2017-11-03 17:02 ` Florian Fainelli
2017-11-03 17:33 ` Tony Lindgren
2017-11-04 8:37 ` Charles Keepax
[not found] ` <20171104083707.gtmnhbrzlqjulwe4-bi+AKbBUZKY6gyzm1THtWbp2dZbC/Bob@public.gmane.org>
2017-11-07 16:00 ` Tony Lindgren
[not found] ` <20171103173353.GJ28152-4v6yS6AI5VpBDgjK7y7TUQ@public.gmane.org>
2017-11-04 12:25 ` Rafael J. Wysocki
2017-11-04 17:19 ` Florian Fainelli
2017-11-07 16:00 ` Tony Lindgren
2017-11-08 0:23 ` Rafael J. Wysocki
2017-11-08 0:28 ` Florian Fainelli
2017-11-08 0:45 ` Rafael J. Wysocki
2017-11-08 1:04 ` Tony Lindgren
2017-11-08 1:02 ` Tony Lindgren
[not found] ` <20171103103707.3e5wb3c7foxbuvvg-bi+AKbBUZKY6gyzm1THtWbp2dZbC/Bob@public.gmane.org>
2017-11-03 17:03 ` Florian Fainelli
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