Subject: about system time incorrect after changing cpu frequency

From: [email-masked] (Viresh Kumar)
Date: Tue, 1 Sep 2015 13:12:05 +0530

On 01-09-15, 15:21, vichy wrote:
> and I add  PLAT_gt_change_freq in arm_global_timer.c like below:
>  PLAT_gt_change_freq calling() {
>     gt_clk_rate = get_periph_clk();
>     clockevents_update_freq(this_cpu_ptr(gt_evt), gt_clk_rate);

In earlier versions of kernel, this had a problem that it works only
for ONESHOT mode and simply returns in PERIODIC mode. I do see that
your's mode is ONESHOT only, and so it should have worked.

Anyway, few prints into that routine to see where we are reaching
might help.

>     __clocksource_updatefreq_hz(&gt_clocksource, gt_clk_rate);

AFAIR, there is a difference between how different mdelay/udelay are
implemented. One of them is using the loops_per_jiffie variable to
calculate the time, other uses clkevt device. I am not 100% sure about
the theory, but that's what I remember. So, have a look from that
perspective as well..

-- 
viresh