about system time incorrect after changing cpu frequency

[Viresh Kumar]

On Mon, Aug 31, 2015 at 7:33 PM, vichy <vichy.kuo at gmail.com> wrote:
> hi all:
> My platform is like below:
> 1. single core Cortex A9
> 2. use global timer for system timer
>
> after I porting cpu frequency driver based on snow ball, the cpu
> frequency did change as I expected.
> But the system time is incorrect( since pherial clk is got from cpu frequency)
>
> for example:
> a) cpu 1G (pherial clk = 250M) --> sleep 1 sec (OK)
> b) cpu 500M  (pherial clk = 125M) --> sleep 1 sec (will be measured as 2 sec)
>
> I try to call below 2 functions to change the frequency of clocksource
> and clockevent, but the above b) sleep time is still incorrect when
> cpu runs in 500Mhz.
>     clockevents_update_freq(this_cpu_ptr(gt_evt), gt_clk_rate);
>     __clocksource_updatefreq_hz(&gt_clocksource, gt_clk_rate);
>
> in Arm cortex A9 single core system with Global timer as system timer,
> is there any kernel api to change system timer period when cpu/pherial
> frequency change?
>
> appreciate your kind help in advance,

The list cpufreq at vger.kernel.org is the wrong list for posting cpufreq queries
as we have moved to Linux PM list <linux-pm at vger.kernel.org> list now.

Try unsetting CPUFREQ_CONST_LOOPS flag in your driver, if you have it
set.