about system time incorrect after changing cpu frequency

[vichy]

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,