linux-kernel - Re: [PATCH 00/11] drivers: Add Pinctrl PM support

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Date:	Wed, 5 Jun 2013 14:41:29 +0200
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Kevin Hilman <khilman@...aro.org>
Cc:	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Hebbar Gururaja <gururaja.hebbar@...com>,
	Grant Likely <grant.likely@...aro.org>,
	Rob Herring <rob.herring@...xeda.com>,
	"davinci-linux-open-source@...ux.davincidsp.com" 
	<davinci-linux-open-source@...ux.davincidsp.com>,
	"devicetree-discuss@...ts.ozlabs.org" 
	<devicetree-discuss@...ts.ozlabs.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Vaibhav Bedia <vaibhav.bedia@...com>, sudhakar.raj@...com
Subject: Re: [PATCH 00/11] drivers: Add Pinctrl PM support

On Tue, Jun 4, 2013 at 8:15 PM, Kevin Hilman <khilman@...aro.org> wrote:
> [Me]
>> I think this will save a *lot* of identical code in all the
>> drivers, that will just have to call
>> pinctrl_select_pm_sleep(), pinctrl_select_pm_default()
>> pinctrl_select_pm_idle() instead of all the complex code.
>>
>> This is what I planned to do but never got around to.
>
> What about taking it one tiny step further, and having it done by the PM
> core itself?

Maybe so, but atleast currently we cannot do it
exclusively in the PM core.

We have things like what you find in
drivers/tty/serial/amba-pl011.c
where pl011_shutdown() puts the pins into sleep mode
on unused TTYs.

The same applies to any unused ports like that, we're
thinking of a way to sleep pins for unused I2C hosts
for example.

And that works fine also on systems that does not
enable CONFIG_PM (so the pin control subsystem
is completely orthogonal). But maybe that is
complicating things? I was just thinking it was a bit
thick to require everything and its dog to make a
complete transition to (runtime)PM.

Yours,
Linus Walleij
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