linux-kernel - Re: [PATCH 2/2] pinctrl: single: Allow indicating loss of pin states during low-power

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Date:   Mon, 25 Sep 2017 12:15:49 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Linus Walleij <linus.walleij@...aro.org>,
        Florian Fainelli <f.fainelli@...il.com>,
        ext Tony Lindgren <tony@...mide.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Stephen Warren <swarren@...dia.com>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Al Cooper <alcooperx@...il.com>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        bcm-kernel-feedback-list <bcm-kernel-feedback-list@...adcom.com>
Subject: Re: [PATCH 2/2] pinctrl: single: Allow indicating loss of pin states
 during low-power

On 09/22/2017 06:03 AM, Linus Walleij wrote:
> On Thu, Sep 21, 2017 at 3:04 AM, Florian Fainelli <f.fainelli@...il.com> wrote:
> 
>> Some platforms (e.g: Broadcom STB: BMIPS_GENERIC/ARCH_BRCMSTB) will lose
>> their register contents when entering their lower power state. In such a
>> case, the pinctrl-single driver that is used will not be able to restore
>> the power states without telling the core about it and having
>> pinctrl_select_state() check for that.
>>
>> This patch adds a new optional boolean property that Device Tree can
>> define in order to obtain exactly that and having the core pinctrl code
>> take that into account.
>>
>> Signed-off-by: Florian Fainelli <f.fainelli@...il.com>
> 
> If we use this per-controller approach rather than the per-state approach
> I discuss in reply to patch 1/2, we should probably make it a generic
> property for pin controllers and not just a pinctrl-single business.

I suppose it makes sense to make this a generic pinctrl property then.
drivers/pinctrl/core.c does not appear to be trying to fetch any
properties for a pinctrl device, but that is probably not too hard to add.

> 
> So patch pinctrl-bindings.txt and put the code somewhere in
> core.
> 
> But that is more of a detail, first we need to figure out how to
> handle this business in general.

Fair enough.
-- 
Florian