Re: VDD1 voltage after resume from idle

[Kevin Hilman <khilman@deeprootsystems.com>]

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.