linux-kernel - Re: [PATCH 2/3] ARM: OMAP2+: omap

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Message-ID: <20130717153838.GJ7656@atomide.com>
Date:	Wed, 17 Jul 2013 08:38:38 -0700
From:	Tony Lindgren <tony@...mide.com>
To:	Grygorii Strashko <grygorii.strashko@...com>
Cc:	Kevin Hilman <khilman@...aro.org>,
	linux-arm-kernel@...ts.infradead.org, linux-omap@...r.kernel.org,
	linux-kernel@...r.kernel.org, devicetree-discuss@...ts.ozlabs.org,
	Linus Walleij <linus.walleij@...aro.org>,
	Stephen Warren <swarren@...dotorg.org>
Subject: Re: [PATCH 2/3] ARM: OMAP2+: omap_device: add pinctrl handling

* Grygorii Strashko <grygorii.strashko@...com> [130717 04:49]:
> Before switching to DT pinctrl states of OMAP IPs have been handled by hwmod
> framework. After switching to DT-boot the pinctrl handling was dropped from
> hwmod framework and, as it was recommended, OMAP IP's drivers have to be updated
> to handle pinctrl states by itself using pinctrl_pm_select_xx() helpers
> (see http://lists.infradead.org/pipermail/linux-arm-kernel/2013-June/173514.html)
> 
> But this is not right for OMAP2+ SoC where real IPs state is controlled
> by omap_device core which enables/disables modules & clocks actually.

I'm not convinced we should try to handle this in a generic way
as only some devices need dynamic remuxing of some pins.

> For example, if OMAP I2C driver will handle pinctrl state during system wide
> suspend the following issue may occure:
> - suspend_noirq - I2C device can be still active because of PM auto-suspend
>   |-_od_suspend_noirq
>      |- omap_i2c_suspend_noirq
>         |- PINs state set to SLEEP
>   |- pm_generic_runtime_suspend
>      |- omap_i2c_runtime_suspend()
>         |- PINs state set to IDLE  <--- *oops* PINs state is IDLE and not SLEEP
>   |- omap_device_idle()
>      |- omap_hwmod_idle()
>         |- _idle()
>            |- disbale module (sysc&clocks)

And in this example you are assuming that you need separate idle and
sleep states, which is not true at least for most cases I've seen.

It is possible that am33xx needs separate idle and sleep states, but
most likely only for some pins. For omap[345] we can get away with
just the default state for most cases.

Regards,

Tony
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