[PATCH v2 00/15] Make SMP timers standalone

[Russell King - ARM Linux]

On Wed, Jan 04, 2012 at 05:39:16PM +0000, Marc Zyngier wrote:
> On 22/12/11 19:32, Russell King - ARM Linux wrote:
> > You're also aware I assume that local timers are different from the global
> > timer itself, and require to have additional callbacks for broadcasting
> > the global timer tick?
> 
> I was under the impression that we either have the global timer together
> with broadcasting or the local timers. Completely removing the broadcast
> callback doesn't seem to generate any ill effect as long as the local
> timers are used instead of the global timer (which of course requires
> broadcast in the SMP configuration).

I believe even if you have local timers, there are situations where the
these will be disabled and the kernel will switch to broadcasting from a
global timer tick.  I think such a scenario would be like that encountered
with OMAP, where suspending a CPU stops its TWD - meaning that the TWD
can't be used to wake the CPU from one of the deeper idle states.