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

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Date:	Tue, 15 Nov 2011 11:07:40 -0800
From:	Stephen Warren <swarren@...dia.com>
To:	Thomas Abraham <thomas.abraham@...aro.org>
CC:	Linus Walleij <linus.walleij@...aro.org>,
	Inderpal Singh <inderpal.singh@...aro.org>,
	"linux-samsung-soc@...r.kernel.org" 
	<linux-samsung-soc@...r.kernel.org>,
	"kgene.kim@...sung.com" <kgene.kim@...sung.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"patches@...aro.org" <patches@...aro.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] ARM: SAMSUNG: Save/restore GPIO drive strength across
 suspend/resume

Thomas Abraham wrote at Monday, November 14, 2011 12:37 PM:
...
> I am not sure how this works, but with dynamic transitioning, will it
> be possible to program the pinmux registers dynamically when a
> driver/controller decides to idle for sometime and come back up again
> (not a system wide suspend-resume cycle). There might be a need for
> the driver to inform the pinmux subsystem of this case and allow the
> pinmux subsystem to re-program pinmux registers as required.

Well, such a feature doesn't exist yet.

But, I envisaged extending the existing:

pmx = pinmux_get()
pinmux_enable(pmx)
...
pinmux_disable(pmx)
pinmux_put(pmx)

to something like:

pmx = pinmux_get(active)
pinmux_enable(pmx)
...
pinmux_switch(suspend)
...
pinmux_switch(active)
...
pinmux_disable(pmx)
pinmux_put(pmx)

(I think LinusW proposed an alternative a while back last time we talked
about this)

This has received only limited discussion though, and there are probably
many gotchas to think through; I imagine any such feature is a way off.

-- 
nvpublic

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