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From"Rafael J. Wysocki" <>
SubjectRe: [linux-pm] [RFC][PATCH] PM: Introduce core framework for run-time PM of I/O devices (rev. 8)
DateSat, 11 Jul 2009 13:08:42 +0200
On Thursday 09 July 2009, Mahalingam, Nithish wrote:
> Hi,

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@rowland.harvard.edu> 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.

Best,
Rafael


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