Re: [PATCH] ARM: architected timers: Mark the clockevent with the C3_STOP feature

["Shilimkar, Santosh" <santosh.shilimkar@xxxxxx>]

On Wed, Jul 4, 2012 at 3:56 PM, Russell King - ARM Linux
<linux@xxxxxxxxxxxxxxxx> wrote:
>
> On Wed, Jul 04, 2012 at 03:24:33PM +0530, Santosh Shilimkar wrote:
> > ARM arch timers stop in low power state and hence can not wakeup CPUs in
> > deeper idle states when used as cloc event devices. Marking these clock
> > event
> > devices with C3_STOP so that during lowpower states, the tick is managed
> > by
> > wakeup capable broadcast timer.
>
> Will tells me that the arch timers don't stop in low power modes, they
> just can't produce wakeup events.  Apparantly the spec says:
>
>    The system counter must be implemented in an always-on power domain.
>    Use of lower-frequency modes must not affect the implemented accuracy.
>
> Are you sure your above description of the problem is correct?

Yes. Will is right.
The arch timers don't stop with a real time counter implementation.
The issue is they are not wakeup capable hence you need a broad-cast switching
which in turn needs C3_STOP.

Regards
Santosh

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