[PATCH 3/5] ARM: twd: Add context save restore support

Thomas Gleixner tglx at linutronix.de
Tue Jan 25 09:12:24 EST 2011

On Tue, 25 Jan 2011, Russell King - ARM Linux wrote:
> On Tue, Jan 25, 2011 at 02:23:10PM +0100, Thomas Gleixner wrote:
> > In which way? I mean the generic code issues a call to the set_mode
> > function when we leave the broadcast mode. So what should the generic
> > code do more ?
> I can't say because these patches only add the hooks, there's no
> implementation yet which uses the hooks.
> Given the description about _why_ those hooks are necessary, it seems
> that something is required.  Either we start adding custom hacks to
> each clockevent driver as is done with this patch, or we get some
> generic help in place.
> I'm not thrilled by the custom hack approach - and I thought the
> clockevent stuff was created to stop this kind of thing happening.

Yes, and it does the right thing:

     idle enter (where the cpu local tick device stops)


		clockevents_set_mode(dev, CLOCK_EVT_MODE_SHUTDOWN)
		tick_broadcast_set_event(dev->next_event, 1)

    idle exit


		clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT)
		tick_program_event(dev->next_event, 1)

So the generic code has all the calls in place. If a clock chip
implementation misses to set control registers in the
CLOCK_EVT_MODE_ONESHOT case, then it's not a short coming of the
generic code which needs magic hooks in the arch code.

The same applies for the periodic mode switch, which is handled via

Am I missing something ?



More information about the linux-arm-kernel mailing list