Re: VDD1 voltage after resume from idle

[Jean Pihet <jpihet@mvista.com>]

On Friday 20 November 2009 20:11:26 Kevin Hilman wrote:
> Jean Pihet <jpihet@mvista.com> writes:
> > Hi Kevin,
> >
> > On Friday 20 November 2009 19:29:02 Kevin Hilman wrote:
> >> Maxime Petazzoni <mpetazzoni@mvista.com> writes:
> >> > Hi,
> >> >
> >> > * Premi, Sanjeev <premi@ti.com> [2009-11-20 21:17:04]:
> >> >> I am facing a strange problem on OMAP3EVM after resuming from idle.
> >> >> When using OPP5, the VDD1 voltage ramps to 1.35V.
> >> >>
> >> >> However, when i go thru the idle/wakeup cycle, the voltage never
> >> >> ramps back to 1.35V but stays at 1.20V.
> >> >
> >> > I'm seeing some interesting behavior with the OPP values here, too,
> >> > with suspend/resume. I'm using SRF based PM and CPUFREQ. Here's what
> >> > happens:
> >> >
> >> > When changing the CPU frequency through the scaling_setfreq knob of
> >> > CPUFREQ, the vdd{1,2}_opp values are updated accordingly. After a
> >> > suspend/resume cycles, the OPPs return to their pre-suspend values,
> >> > all is fine.
> >> >
> >> > But when changing the OPP values by hand through the vdd{1,2}_opp
> >> > knobs, the CPU frequency is changed accordingly, which is expected.
> >> > But after a suspend/resume cycle, the OPP values return to the value
> >> > CPUFREQ set them to (which may be different than the default OPP
> >> > values of 3).
> >> >
> >> > Is this the normal behavior? Is cpufreq authoritative on the OPP
> >> > values on resume? Or should it follow whatever value was manually set
> >> > before suspending?
> >>
> >> FWIW, the vdd*_opp sysfs hooks were for initial debug/dev and should
> >> be considered experimental (a.k.a broken.) They will disappear from
> >> the PM branch shortly.
> >>
> >> CPUfreq should be the only interface used for DVFS.
> >
> > Could the PM page on elinux.org be updated with that info? I am proposing
> > to change it before you ask me ;p
>
> Done.
>
> I added the following note to the 'opp control' section.
>
> OPP control via sysfs is deprecated. Please use CPUfreq interfaces for
> DVFS.
Thanks!

Jean