Re: Changes to power management in ehci-tegra

[Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>]

On Fri, 13 Apr 2012, Stephen Warren wrote:

> > If you do:
> > 
> > 	echo auto >/sys/devices/.../power/control
> > 
> > (where the ... gets filled in with the path to the EHCI controller),
> > then the controller should automatically get powered down whenever the
> > bus does.  The bus will get powered down whenever no USB devices are
> > plugged in (or the only attached USB devices are things like hubs that
> > will themselves get suspended) after a 2-second delay.
> 
> One small issue with the patch: There are two copies of
> tegra_ehci_resume(). I assume the second should be renamed
> tegra_ehci_runtime_resume().

Whoops!  You're right, of course.  I'll update my patch.

> I've tested the patch, and can unplug a USB device, wait 10 seconds,
> then plug it back in, and everything works as expected.
> 
> However, I don't notice /sys/devices/.../power/runtime_status ever
> saying anything other than active, and I can't cat autosuspend_delay_ms,
> so I assume I'm still not triggering the path you want me to test. I do
> have PM_RUNTIME turned on. Any ideas? Do I need some patch to the USB
> core to enable this? I tested on next-20120413 plus a few local patches.

autosuspend_delay_ms isn't relevant here; the controller should be 
suspended with no delay as soon as the root hub suspends.  No other 
patches should be needed; it sounds like you're doing everything right.

If you enable CONFIG_PM_ADVANCED_DEBUG along with CONFIG_PM_RUNTIME, 
what do all the other power/runtime_* files show?

Alan Stern

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