Re: [PATCH 2/2] ARM: omap: timers: reduce rating of gp_timer clocksource

[Grygorii Strashko]

On 12/02/2016 10:47 AM, Tony Lindgren wrote:
> * Grygorii Strashko <grygorii.strashko@xxxxxx> [161129 08:43]:
> > On 11/24/2016 12:19 AM, Keerthy wrote:
> > > From: Grygorii Strashko <grygorii.strashko@xxxxxx>
> > >
> > > Now ARM Global timer (rating 300) will not be selected as clocksource,
> > > because it's initialized after OMAP GP Timer (rating 300) and
> > > Timekeeping core will not allow to replace clocksource with new one if
> > > both of them have the same rating.
> > >
> > > Reduce rating of OMAP GP Timer (300->290) when it's used as
> > > clocksource device - this will allow to select ARM Global timer (300)
> > > as clocksource when enabled.
> > >
> > > Signed-off-by: Grygorii Strashko <grygorii.strashko@xxxxxx>
> > > Signed-off-by: Dave Gerlach <d-gerlach@xxxxxx>
> > > Signed-off-by: Keerthy <j-keerthy@xxxxxx>
> >
> > Unfortunately, this patch has dependency [1] and can't be used alone as
> > it will cause ARM Global timer to be selected as clocksource
> > always on am437x and this will kill cpuidle, because ARM Global timer
> > is not in always_on domain.
> >
> > The intention of enabling ARM Global timer is only for non-pm aware use
> > cases for RT-kernel latency improvement - where deep cpuidle states are not
> > enabled.
>
> Yeah we need to fix up things to be able to change the clocksource
> in addition to clockevent. However, currently only cpuidle_coupled
> knows when the whole system is idle, so quite a bit of work is
> needed to do that in a sane way.

Also sched_clock and timer_delay ;)


> What about the first patch in this series?

Fist one is ok. It was originally posted long time ago.

--
regards,
-grygorii