Re: So, what's the status on the recent patches here?

Alexey Starikovskiy
2006-08-18T15:29:31Z

Igor Stoppa wrote:
> On Fri, 2006-08-18 at 00:39 +0300, ext Pavel Machek wrote:
>> Hi!
>>
>>>> If there are dependancies inherently linking core1 and core2,
>> cpufreq
>>>> should already be programming both parts. For example, the SA1100
>>>> driver programs both CPU and SDRAM controller. If there isn't any
>>>> dependancy
>>>> between them, I don't see the attraction of creating an artificial
>> one
>>>> in the way suggested for no real purpose.
>>>>
>>>> Things like voltage and frequency are closely tied together, so
>>>> offering
>>>> any means of controlling them independantly makes no sense afaics.
>>> Yet a certain subsystem (for example an onboard camera, in a phone)
>>> might require a higher voltage when it's active, effectively
>> loosening
>>> the tight coupling between freq and voltage that the porcessor is
>>> enforcing.
>> So... you expect userland to echo high > state before camera can be
>> used?
>>
>> I'd rather have kernel automagically up the voltage when /dev/video0
>> is opened...
>
> Not really, I meant that the CPU is not the only customer of power
> domains (depend on the HW design), so the relation freq <-> voltage is
> not always true.
>
Then you need to introduce power domains and associate your devices with them, isn't it?
So if your camera appears in the same domain with CPU, the voltage of
that domain will go up either with camera=on, or CPU going to higher frequency.