RE: [linux-pm] [PATCH] i2c: OMAP: fix static suspend vs. runtime suspend

[Rajendra Nayak <rnayak-l0cyMroinI0@public.gmane.org>]

> -----Original Message-----
> From: Alan Stern [mailto:stern-nwvwT67g6+6dFdvTe/nMLpVzexx5G7lz@public.gmane.org]
> Sent: Monday, January 31, 2011 8:43 PM
> To: Rajendra Nayak
> Cc: Kevin Hilman; Ben Dooks; linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org;
linux-pm-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org; linux-
> omap-u79uwXL29TY76Z2rM5mHXA@public.gmane.org; linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org
> Subject: Re: [linux-pm] [PATCH] i2c: OMAP: fix static suspend vs.
runtime suspend
>
> On Mon, 31 Jan 2011, Rajendra Nayak wrote:
>
> > Can you elaborate a bit more on how/why runtime PM transitions
> > are disabled during system suspend, and how is it taken care
> > of that a runtime resume of a device works however a subsequent
> > runtime (re)suspend does not?
>
> I'll answer for Kevin.  This is done by the PM core, in order to
> prevent runtime power transitions from interfering with a system power
> transition.  The PM core increments the device's usage_count; this
> prevents the device from being runtime-suspended but it allows
> runtime-resume calls to go through.

Thanks, I did remember seeing the pm_runtime_get_noresume()
in dpm_prepare(). Just did not correlate it was the same Kevin
was trying to say.

Regards,
Rajendra

>
> Alan Stern