linux-kernel - Re: [PATCH] ARM: SAMSUNG: Save/restore GPIO drive strength across suspend/resume

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Date:	Sat, 12 Nov 2011 12:00:20 +0100
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Inderpal Singh <inderpal.singh@...aro.org>
Cc:	linux-samsung-soc@...r.kernel.org, kgene.kim@...sung.com,
	linux-arm-kernel@...ts.infradead.org, patches@...aro.org,
	Stephen Warren <swarren@...dia.com>,
	linux-kernel@...r.kernel.org,
	Thomas Abraham <thomas.abraham@...aro.org>
Subject: Re: [PATCH] ARM: SAMSUNG: Save/restore GPIO drive strength across suspend/resume

On Sat, Nov 12, 2011 at 6:01 AM, Inderpal Singh
<inderpal.singh@...aro.org> wrote:

> GPIO driver strength settings are not preserved across suspend/resume
> for s5pc100, s5pv210 and Exynos platforms which has been the cause of
> mmc/sd card read/write failures after resume. Fix this by saving and
> restoring the GPIO driver strength register settings across suspend/resume.
>
> Signed-off-by: Inderpal Singh <inderpal.singh@...aro.org>

On a related theme: I am thinking about how to support preserving
drive strength (etc) across suspend/resume and deepsleep in the
pincontrol subsystem.

Currently I am playing with the idea to let pin groups have states,
as the different configurations seem to be 90% or so about very
specific sleep modes, so say:

pinconf_set_group_state("mmcgroup", PINCONF_STATE_ACTIVE);
pinconf_set_group_state("mmcgroup", PINCONF_STATE_SUSPENDED);
pinconf_set_group_state("mmcgroup", PINCONF_STATE_SLEEP);

This would then instruct each pin controller driver to configure
each pin apropriately for the given state, and that cross-references
to a table keeping track of the preset per-pin for each state.

My intuitive idea is that letting the core keep track of the state of
every pin and letting pin groups harness the settings for a group
of pins is the proper approach to the problem.

Do you think something like this will work for the S5P:s?

Yours,
Linus Walleij
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