Colibri PXA320 Power management question

[Haojian Zhuang]

On Mon, Sep 6, 2010 at 7:30 PM, Mark Brown
<broonie at opensource.wolfsonmicro.com> wrote:
> On Mon, Sep 06, 2010 at 07:09:44PM +0800, Eric Miao wrote:
>> On Mon, Sep 6, 2010 at 6:13 PM, Mark Brown
>
>> > That'd be slightly entertaining, though, since IIRC the hardware
>> > implementation isn't really set up for being constrained - it doesn't
>> > expect to be cooperating with software governors.
>
>> It doesn't need to. There is actually an internal command table, and
>> not really sure about the mapping scheme though, but when software
>> then has only to care about the frequencies, and voltages will be
>> adjusted accordingly.
>
> Ah, I'm misremembering the PXA implementation for the i.MX one - the
> i.MX version of this feature had a governor rather than just doing a
> lookup from the frequency to a voltage.
>
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I think that the key isn't scaling voltage. We can enable both
auto-scaling (hardware) and software-scaling voltage in cpufreq
driver. The key point is that device may occur fails while scaling
frequency in device working mode. I remember that cpufreq doesn't care
about this behavior.