On 13 October 2010 16:14, Amit Kucheria <amit.kuche...@linaro.org> wrote:
> On Wed, Oct 13, 2010 at 4:35 PM, Vincent Guittot
> <vincent.guit...@linaro.org> wrote:
>> Hi,
>>
>> Exporting the clock tree state is help us to monitor clocks state and
>> to find the guilty clocks. But could it be also possible to have a
>> write access to the clock tree ? During power consumption optimization
>
> That is an interesting idea.
>
>> step, we need to identify clock/regulator which should be disable but
>> we also want to know what will be the gain. Instead of waiting for the
>> new code with the right clock management, we generally want to
>> directly disable it and look at the 1st result. It will be also useful
>> when we are looking for the best clock tree configuration without
>> developing/modifying a lot of source code.
>
> Do you anticipate any other interface besides making the 'rate' sysfs
> file RW and controlling the clock by writing various rates to the
> file?
>
> So,
> 0 - clock off
> any other positive value - round down to the nearest valid rate
>
> and writing to the file would lead to a call to clk.set_rate()
>

my idea is to export the clock interface through the debugfs for the
optimization phase. Then each machine implements and exports the
supported function.

>> For sure, such kind of feature is quite dangerous and must be enable
>> carefully but it would help for optimizing power consumption.
>
> I'm not sure that all clock frameworks are even ready for this feature
> today, especially if they don't handle recalculation of child clock
> rates as part of set_rate().
>
> /Amit
>

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