Re: [PATCH] clocksource/arm_global_timer: reconfigure clockevents after cpufreq change

[Thomas Gleixner]

On Tue, 29 Nov 2016, Alexander Kochetkov wrote:

> After a cpufreq transition, update the clockevent's frequency
> by fetching the new clock rate from the clock framework and
> reprogram the next clock event.

The frequency change would not only affect the clockevent device, it also
would affect the clocksource. So the patch is incomplete, but see below.

> The clock supplying the arm-global-timer on the rk3188 is coming
> from the the cpu clock itself and thus changes its rate everytime
> cpufreq adjusts the cpu frequency.

That's broken and the clk framework should keep the CORE_PERI clock at a
constant rate by reprogramming the divider of the CPU clock.

> Found by code review, real impact not known. Assume what actual
> HZ value will be different from expected on platforms using
> arm-global-timer as clockevent.

Assumptions w/o real impact are a perfect reason not to apply that
patch. This want's a proper proof that the global timer really changes and
this hackery is required, which I seriously doubt.

Thanks,

	tglx