linux-kernel - Re: [RFC] pinctrl: pinctrl-imx: implement suspend/resume

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Message-ID: <9333041871b27a3099b185e26b564e2a@agner.ch>
Date:	Thu, 04 Jun 2015 22:24:57 +0200
From:	Stefan Agner <stefan@...er.ch>
To:	Zhi Li <lznuaa@...il.com>, Linus Walleij <linus.walleij@...aro.org>
Cc:	Shawn Guo <shawn.guo@...escale.com>,
	Sascha Hauer <kernel@...gutronix.de>,
	Uwe Kleine-König <u.kleine-koenig@...gutronix.de>,
	kernel list <linux-kernel@...r.kernel.org>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [RFC] pinctrl: pinctrl-imx: implement suspend/resume

On 2015-06-04 17:00, Zhi Li wrote:
> On Mon, Jun 1, 2015 at 10:12 AM, Stefan Agner <stefan@...er.ch> wrote:
<snip>
>> If no other SoC is making use of it, its probably better to implement
>> it in the SoC specific code (e.g. pinctrl-vf610.c?) Although, currently
>> the mapped access to the registers is only locally available in
>> pinctrl-imx.c.
> 
> i.MX7 support LPSR mode, which IOMUX will lost state also.
> 

Thanks for the information, good to know.

>>
>> I'm also not sure if the suspend/resume functions are currently
>> early enough, at least the noirq family of suspend/resume functions
>> would be earlier. Hence if a device needs to have access to pins then,
>> we would restore them too late. Maybe syscore_ops would be more
>> appropriate?
> 
> Driver can call pinctrl_pm_select_sleep_state in suspend and
> pinctrl_pm_select_default_state
> to recover IOMUX state.
> 
> but I think this way is more simple than driver call
> pinctrl_pm_select_default_state.
> 

I actually tried to experiment with pinctrl_pm_select_default_state and
pinctrl_pm_select_sleep_state. I think, one solution would be to create
sleep states for all drivers. However, it's not necessary to change to a
sleep state, since the controller looses the state anyway. What would be
required is having a function which allows to force the default state
for all pinctrl settings... As far as I can tell, there is no such
functionality currently...? Linus?

--
Stefan

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