RE: [linux-pm] [RFC][PATCH] PM: Introduce core framework forrun-time PM of I/O devices (rev. 8)

[Mahalingam, Nithish]

>Hi,
>
>> I am newbee to this mailing list. Please excuse me if I am talking nonsense here.
>> 
>> 
>> 
>> On Thu, Jul 9, 2009 at 10:48 PM, Alan Stern<stern@xxxxxxxxxxxxxxxxxxx> wrote:
>>>> On Thu, 9 Jul 2009, Magnus Damm wrote:
>>>>
>>>> Clocks should be stopped as soon as possible without any delay. The
>>>> clock stopping is very cheap performance wise. Also, the clock
>>>> stopping is done on bus level without invoking any driver callbacks.
>>>>> Delaying the clock stopping does not make any sense to me.
>>>>
>>>> In that case the device driver or bus subsystem should manage the
>>>> device's clock directly.  There's no need to tie it in with the runtime
>>>> PM framework.  Simply start the clock before each I/O operation and
>>>> stop it afterward.
>> 
>>> It's not that easy. The clock needs to be enabled to let the hardware
>>> device perform device specific stuff. For instance, the clock for the
>>> LCD controller needs to be on to redraw the screen. When the driver
>>> knows that it's done with the clock it can notify the bus using
>>> Runtime PM.
>> 
>> Is there any plan to look into the "Clock Framework" that was developed as
>> part of OMAP and extending this to make it generic for all platforms?

>I don't have any plan to do that and I heaven't heard of anyone planning to do
>it.

Thanks for the reply Rafael. I felt if we are talking about controlling a device clock from a runtime PM framework we should look at extending the Clock framework rather than re-inventing things.

Regards,
Nithish Mahalingam
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