Re: [EXT] Re: Ask for help about cpufreq issue

[Viresh Kumar <viresh.kumar@linaro.org>]

On 07-02-20, 06:03, Andy Tang wrote:
> Hi Viresh,
> 
> I have tried performance governor, cpu frequency is at the lowest frequency.
> I also tried ondemand governor with high cpu load, cpu frequency doesn't increase too.
> 
> root@localhost:~# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
> performance
> root@localhost:~# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies
> 1600000 1000000 800000 500000
> root@localhost:~#
> root@localhost:~# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq
> 500000
> 
> root@localhost:~# cat /sys/devices/system/cpu/cpufreq/policy0/stats/*
> cat: /sys/devices/system/cpu/cpufreq/policy0/stats/reset: Permission denied
> 1600000 214
> 1000000 91
> 800000 82
> 500000 480088
> 240
>    From  :    To
>          :   1600000   1000000    800000    500000
>   1600000:         0        15        10        10
>   1000000:        21         0        22        18
>    800000:         6        23         0        44
>    500000:         7        23        41         0

See, frequencies are getting changed according to this table (at least
from cpufreq's point of view), which means that cpufreq transitions
are passing just fine.

I just had a look at the driver and may have some idea on what's going
on. The cpufreq driver doesn't program the frequencies, but instead it
just switches the parent clk for changing the frequency. And when you
try to read the frequency, all we do is read the frequency from the
clk pointer using clk_get_rate().

So, here are the things which can go wrong, in order of how I would
like to debug them.

- The frequency of all parent clocks is set to 500 MHz by someone and
  so clk_get_rate() always report that despite changes to the stats
  table.

- clk_set_parent() isn't setting the parent correctly.

Try putting some print messages to the driver to see if target_index()
routine is able to set the parent clk properly or not.

-- 
viresh