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

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Date:	Fri, 31 May 2013 11:08:06 -0700
From:	Kevin Hilman <khilman@...aro.org>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:	Hebbar Gururaja <gururaja.hebbar@...com>, grant.likely@...aro.org,
	linus.walleij@...aro.org, rob.herring@...xeda.com,
	davinci-linux-open-source@...ux.davincidsp.com,
	devicetree-discuss@...ts.ozlabs.org,
	linux-arm-kernel@...ts.infradead.org, linux@....linux.org.uk,
	linux-kernel@...r.kernel.org, vaibhav.bedia@...com,
	sudhakar.raj@...com, Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [PATCH 00/11] drivers: Add Pinctrl PM support

+ Linus W. (pinctrl maintainer)

Dmitry Torokhov <dmitry.torokhov@...il.com> writes:

> Hi Hebbar,
>
> On Fri, May 31, 2013 at 03:43:00PM +0530, Hebbar Gururaja wrote:
>> By optionally putting the pins into sleep state in the suspend [or in
>> runtime_suspend] callback we can accomplish two things.
>> - One is to minimize current leakage from pins and thus save power,
>> - second, we can prevent the IP from driving pins output in an
>> uncontrolled manner, which may happen if the power domain drops the
>> domain regulator.
>> 
>> These states can be specified in the DT blob and corresponding driver
>> can pick these states during probe & set the related values during
>> idle/suspend.
>> 
>> Not all drivers support/has idle state. Drivers like i2c, spi, mmc has
>> idle states and hence these drivers are updated to support all the
>> three states
>> - default  : during regular operation
>> - idle : when the module is in idle state
>> - sleep : when the module is in suspend state
>> 
>> For those drivers which doesn't support/have idle state (at least at
>> the moment), only default & sleep state is added.
>
> As with the original introduction of pinctrl states my question is: "Can
> all of this be handled in the driver/bus core instead of adding a lot
> of boilerplate code to the individual drivers".

Yes, I had the same thought.

What's being handled here are either events related to runtime PM
(runtime suspend, runtime resume) or system PM (suspend/resume) so seems
appropriat to handle them in the PM core.

Kevin
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