[PATCH v1] ARM: clocksource: make ARM_GLOBAL_TIMER selectable

[linux@arm.linux.org.uk (Russell King - ARM Linux)]

On Wed, Apr 27, 2016 at 04:31:05PM +0300, Grygorii Strashko wrote:
> Sorry, but this patch doesn't disable anything. It provides possibility
> to do a custom build with disabled ARM GT driver without Kernel code
> modification - in my case RT-kernel and non-RT Kernel should run on same
> HW and RT kernel should use ARM GT as clocksource/sched_clock, but 
> non-RT Kernel shouldn't.
> 
> I think RT can't be part of single zImage - it make no sense.
> 
> > 
> > Maybe a linux-specific property is needed here - "linux,low-power-unstable"
> > or something like that?
> > 
> 
> I've tried smth. like this [1]
> 
> And it is not "unstable", it's will just stop in C3 (CPUIdle) and there no possibility 
> (at least I've not found how to do this) to adjust Freq in case of CPUFreq.
> [above is about clocksource/sched_clock]
> 
> [1] http://lists.infradead.org/pipermail/linux-arm-kernel/2015-November/386858.html

Don't think I'm going to follow URLs - I don't use a desktop mail
client, and as I'm several days behind with email, I don't have time
to go looking through a crappy pipermail web archive at the moment
either.

Anyway, why can't we use the priority system for clocksources?  If
ARM GT is problematical, we need a way to register it with a lower
priority than the preferred time keeping source.  That's exactly
what the clocksource priority field is for.

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