Question about frequencies with Banana Pi (A20)

[vlad59]

Hi,

 

No real problem, just a question. I'm using latest Armbian Jessie 5.25 with my good old Banana Pi.

root@marvin:~# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies
144000 312000 528000 720000 864000 912000 960000
root@marvin:~# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_min_freq
480000
root@marvin:~# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq
960000

Please notice that 480MHz (the min freq) is not in the available frequencies.

 

So that gives the following output with cpufreq-info :

root@marvin:~# cpufreq-info
cpufrequtils 008: cpufreq-info (C) Dominik Brodowski 2004-2009
Report errors and bugs to cpufreq@vger.kernel.org, please.
analyzing CPU 0:
  driver: cpufreq-dt
  CPUs which run at the same hardware frequency: 0 1
  CPUs which need to have their frequency coordinated by software: 0 1
  maximum transition latency: 244 us.
  hardware limits: 144 MHz - 960 MHz
  available frequency steps: 144 MHz, 312 MHz, 528 MHz, 720 MHz, 864 MHz, 912 MHz, 960 MHz
  available cpufreq governors: conservative, ondemand, userspace, powersave, performance, schedutil
  current policy: frequency should be within 480 MHz and 960 MHz.
                  The governor "schedutil" may decide which speed to use
                  within this range.
  current CPU frequency is 528 MHz (asserted by call to hardware).
  cpufreq stats: 144 MHz:0,00%, 312 MHz:0,00%, 528 MHz:98,22%, 720 MHz:1,04%, 864 MHz:0,08%, 912 MHz:0,23%, 960 MHz:0,43%  (39367)
analyzing CPU 1:
  driver: cpufreq-dt
  CPUs which run at the same hardware frequency: 0 1
  CPUs which need to have their frequency coordinated by software: 0 1
  maximum transition latency: 244 us.
  hardware limits: 144 MHz - 960 MHz
  available frequency steps: 144 MHz, 312 MHz, 528 MHz, 720 MHz, 864 MHz, 912 MHz, 960 MHz
  available cpufreq governors: conservative, ondemand, userspace, powersave, performance, schedutil
  current policy: frequency should be within 480 MHz and 960 MHz.
                  The governor "schedutil" may decide which speed to use
                  within this range.
  current CPU frequency is 528 MHz (asserted by call to hardware).
  cpufreq stats: 144 MHz:0,00%, 312 MHz:0,00%, 528 MHz:98,22%, 720 MHz:1,04%, 864 MHz:0,08%, 912 MHz:0,23%, 960 MHz:0,43%  (39367)

Should I set /sys/devices/system/cpu/cpu0/cpufreq/scaling_min_freq to 528000 or is there a problem with 480MHz not being in available frequencies ?

 

IIRC I had the same problem with the previous kernel (Armbian 5.24), I do not remember if it happened before.

 

[tkaiser]

You compare cpufreq-utils 'policy' (contents of /etc/default/cpufrequtils) and kernel capabilities (contents of .dts file). Armbian usually sets identical minimum cpufreq policy for all boards of the same SoC family: https://github.com/igorpecovnik/lib/blob/master/config/sources/sun7i.conf#L26

 

And for whatever reasons DT contents for BPi vary (you can search linux-sunxi archives for specific reasons why this and that happens). From a practical point of view there is exactly no difference between 480 MHz and 528 MHz since these 48 MHz are simply negligible

 

You could adjust cpufreq-utils settings but why? Makes no sense unless you use 144 or 312 MHz (which has some drawbacks if you chose ondemand like overall lower CPU performance, should work better with schedutil governor but there are also some problems reported. IIRC audio pops when using schedutil)

[vlad59]

The only thing I wanted to change is to set scaling_min_freq to 528000 for consistency. But it won't change a single thing.

 

Anyway thanks a lot for your answer, my curiosity is satisfied .