Armada 3720 cpufreq bug: request for testing (EspressoBIN, uDPU, ...)

[Marek Behún]

Hello,

I have a request for testing some patches that fix cpufreq issues on
Armada 3720 (EspressoBIN, uDPU, Devel Board, maybe others?).

It concerns top 4 commits of branch a3720-cpufreq-issues of repository
https://git.kernel.org/pub/scm/linux/kernel/git/kabel/linux.git/

(log at https://git.kernel.org/pub/scm/linux/kernel/git/kabel/linux.git/log/?h=a3720-cpufreq-issues)

We've discovered a bug in Armada 3720 cpufreq driver that causes
base CPU frequency to drop to 800 MHz on systems configured to 1 GHz.
More info here:
https://www.spinics.net/lists/arm-kernel/msg844752.html

The patchset above led us to discover another bug, in the SOC itself,
that causes the CPU to behave weirdly when frequency changes to 1 GHz.
A similar erratum is documented by Marvell but only for systems where
base frequency is 1.2 GHz.

We've discovered that to make cpufreq scaling stable on Armada 3720
on systems with base frequency 1 GHz, we also have to set voltage levels
for L1, L2 and L3 loads to 1108 mV. (We were led to this by patch we found here
https://forum.armbian.com/topic/10429-how-to-make-espressobin-v7-stable/page/2/?tab=comments#comment-80012).

We would like you to build this sources and test the ondemand cpufreq
governor on systems with variable CPU load, for at least 1 day (more is better).
If you could also test the userspace governor and randomly change frequency,
it would be great.

Please let me know if and when you are willing to do this.

Thank you.

Marek & Pali