[Openpxa-users] Colibri PXA320 Power management question

[eric.y.miao@gmail.com (Eric Miao)]

On Sun, Aug 15, 2010 at 5:13 PM, Igor Grinberg <grinberg@compulab.co.il> wrote:
> On 08/15/10 05:06, Eric Miao wrote:
>> On Sat, Aug 14, 2010 at 2:53 PM, Marek Vasut <marek.vasut@gmail.com> wrote:
>>
>>> Dne ?t 12. srpna 2010 12:02:17 Yuri Ludkevich napsal(a):
>>>
>>>> Hi there :)
>>>>
>>>> I have a question about power management of Colibri PXA320 module:
>>>> I found that bits PVE and FVE in PVCR register are disabled,
>>>> so at frequency change voltage will not change.
>>>>
>>>> If I turn on PVE and FVE with pxaregs tool - voltage changes just fine.
>>>> Where are suitable place in the kernel for PVCR initialization?
>>>>
>>> I believe kernel should handle all that. Eric CCed.
>>>
>>>
>> Yep. Some of the design doesn't use the built-in power I2C at all,
>> they use some non-standard I2C power management IC. So this
>> should be handled in kernel indeed. The currently problem is that
>> we don't yet have a clean framework, some platforms are writing
>> directly to these registers to configure, which should be avoided.
>>
>
> If I recall correctly, the pxa3xx built-in power I2C control is designed
> for use with 100% compatible PMIC chip and if for some reason
> the hardware has another PMIC, which is not 100% compatible,
> then the built-in control can do more harm then good.

Indeed. With some of those incompatible I2C power management ICs,
some are controlling the Power I2C manually with the bits turned off
in PVCR.

>
> I think we need a good and configurable DVFS driver to take care
> of all the power management stuff.
>

Yes.