Dropping "depends on SMP" for HAVE_ARM_TWD -- take 2

Sören Brinkmann soren.brinkmann at xilinx.com
Mon Oct 5 08:13:03 PDT 2015

On Mon, 2015-10-05 at 05:19PM +0530, Afzal Mohammed wrote:
> Hi,
> On Sun, Oct 04, 2015 at 10:46:52PM -0700, Sören Brinkmann wrote:
> > On Sat, 2015-10-03 at 11:12AM +0100, Marc Zyngier wrote:
> > > Indeed, I cannot see any code that does that in the GT driver. But if
> > > you have an A9 MP, you probably want to stick to TWD, which gives you a
> > > per-cpu timer instead of a global timer that will require IPIs to other
> > > CPUs.
> > 
> > I think the TWD only provides a clock_event device. Clocksource and
> > schedclock would have to be provided by something else.
> If no clocksource, sched clock is provided, default jiffies based ones
> would be sufficient for single core, no ?, though not a preferred one.

Yes that is correct. My point was more, that twd+cpufreq is a rather
easy case since it doesn't provide a clocksource/schedclock. A driver
that provides those needs quite some more work if it depends on the CPU
frequency and needs to be usable with cpufreq.


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