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

[Andre Heider]

Hi Marek,

On 09/10/2020 12:57, Marek Behún wrote:
> 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.

Thanks for hunting this one down!

I've applied your 4 patches to v5.9 and gave it a quick spin.

I'm using schedutil, which had the very same issue. It never actually 
switched to 1000mhz. It claimed it did, but the `mhz` util as well as 
the 7z benchmark proved it never used anything >800mhz.

Before:
$ 7z b

7-Zip [64] 16.02 : Copyright (c) 1999-2016 Igor Pavlov : 2016-05-21 

p7zip Version 16.02 (locale=en_US.UTF-8,Utf16=on,HugeFiles=on,64 bits,2 
CPUs LE)

LE
CPU Freq:   793   793   794   793   794   792   793   794 


RAM size:     985 MB,  # CPU hardware threads:   2 

RAM usage:    441 MB,  # Benchmark threads:      2 


                        Compressing  |                  Decompressing 

Dict     Speed Usage    R/U Rating  |      Speed Usage    R/U Rating 

          KiB/s     %   MIPS   MIPS  |      KiB/s     %   MIPS   MIPS 


22:        711   149    464    692  |      17501   194    770   1494 

23:        708   155    465    722  |      17595   198    770   1523 

24:        682   158    464    734  |      17079   196    764   1499 

25:        663   160    473    757  |      15595   189    734   1388
----------------------------------  | ------------------------------
Avr:             156    466    726  |              194    760   1476
Tot:             175    613   1101


After:
$ 7z b

7-Zip [64] 16.02 : Copyright (c) 1999-2016 Igor Pavlov : 2016-05-21
p7zip Version 16.02 (locale=en_US.UTF-8,Utf16=on,HugeFiles=on,64 bits,2 
CPUs LE)

LE
CPU Freq:   992   998   998   994   996   997   997   997

RAM size:     987 MB,  # CPU hardware threads:   2
RAM usage:    441 MB,  # Benchmark threads:      2

                        Compressing  |                  Decompressing
Dict     Speed Usage    R/U Rating  |      Speed Usage    R/U Rating
          KiB/s     %   MIPS   MIPS  |      KiB/s     %   MIPS   MIPS

22:        866   151    559    843  |      22334   198    962   1907
23:        872   152    584    889  |      21809   197    959   1888
24:        808   145    599    869  |      11413   110    915   1002
25:        716   137    596    819  |      21092   198    949   1877
----------------------------------  | ------------------------------
Avr:             146    585    855  |              176    946   1669
Tot:             161    765   1262


The measured frequency as well as the performance data finally looks 
good, so:

Tested-by: Andre Heider <a.heider at gmail.com>

Thanks,
Andre