Re: [PATCH 2/3] ARM: OMAP2+: omap_device: add pinctrl handling

[Grygorii Strashko]

On 07/18/2013 11:14 AM, Tony Lindgren wrote:
> * Grygorii Strashko <grygorii.strashko@xxxxxx> [130717 10:11]:
> > On 07/17/2013 06:38 PM, Tony Lindgren wrote:
> > > * Grygorii Strashko <grygorii.strashko@xxxxxx> [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)

Above call sequence explains what's going on when .suspend_noirq() is 
called - .suspend_noirq() handler ==> _od_suspend_noirq() and it's set 
for all OMAP2+ devices.


> > > 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.
> >
> > I don't need both states (at least right now) :), but
> > - if any OMAP2+ driver will have two states defined: "idle" and "sleep"
> > - and if it will try to manage them from drivers callbacks only using
> >    pure calls to pinctrl_pm_select_xx() helpers
> >
> > the "idle" state will be selected during suspend and *not* "sleep".
>
> But the drivers have separate calls for runtime PM and suspend/resume?

Yes, but for OMAP2+ everything is handled by OMAP device framework :)

> > > 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.
> >
> >
> > In case, if only "default" state is defined for device - nothing will
> >   be done by OMAP device framework for it (I mean any call to
> > pinctrl_pm_select_xx() will do nothing - it just checks that there is
> > no state and returns 0).
>
> If we want to automate something, it should be done at Linux generic
> level rather than at omap "bus" level. That sort of relates to drivers
> needing to know when they've lost context too, which should be
> implemented in Linux generic way.
>
> Regards,
>
> Tony

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