[Letux-kernel] Strange things happening with latest kernels

[H. Nikolaus Schaller]

> Am 17.06.2019 um 21:56 schrieb H. Nikolaus Schaller <hns at goldelico.com>:
> 
> Hi Andreas,
> 
>> Am 15.06.2019 um 18:46 schrieb H. Nikolaus Schaller <hns at goldelico.com>:
>> 
> 
> I have just made another strange observation:
> 
> login: root
> password:
> 
> root at letux:~# ./temperatures 
> Sat Jan 1 00:50:10 UTC 2000 58° 3648mV 800MHz
> root at letux:~# ./temperatures 
> Sat Jan 1 00:50:16 UTC 2000 67° 3642mV 800MHz
> root at letux:~# ./temperatures 
> Sat Jan 1 00:50:18 UTC 2000 67° 3642mV 800MHz
> root at letux:~# ./temperatures 
> Sat Jan 1 00:50:20 UTC 2000 67° 3648mV 800MHz
> root at letux:~# 
> 
> The first call shows a lower temperature and
> with the second the temperature jumps up suddenly
> by 9° and stays there.
> 
> I can try to check with the Thermocamera if it
> really gets hotter...
> 
> Or try this in a loop without some seconds delay
> to see if there is a gradual increase.
> 
> This is with letux-5.2-rc5 on gta04. Please note that
> I forgot to merge the twl4030-opp-fix so that
> I will rebuild letux-5.2-rc5 sources and binaries
> again.

I have done some tests and it seems as if the
first temperature test (even 5 minutes after boot)
is significantly lower than those after:

letux login: root
Password: 
Last login: Sat Jan  1 14:58:38 UTC 2000 on console
Linux letux 5.2.0-rc5-letux+ #296 SMP PREEMPT Tue Jun 18 09:36:52 CEST 2019 armv7l

The programs included with the Debian GNU/Linux system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.

Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
permitted by applicable law.

!!!  LetuxOS WARNING                                                      !!!
!!!  Root access through ssh and console with empty password is enabled.  !!!
!!!  This is a big security hole.                                         !!!
!!!  To disable, run 'apt-get remove letux-ssh-root'                      !!!

root at letux:~# cat /sys/class/thermal/thermal_zone0/temp
53500
root at letux:~# cat /sys/class/thermal/thermal_zone0/temp
62000
root at letux:~# cat /sys/class/thermal/thermal_zone0/temp
62000
root at letux:~# cat /sys/class/thermal/thermal_zone0/temp
62000
root at letux:~# cat /sys/class/thermal/thermal_zone0/temp
62000
root at letux:~# cat /sys/class/thermal/thermal_zone0/temp
62000
root at letux:~# cat /sys/class/thermal/thermal_zone0/temp
62000
root at letux:~# cat /sys/class/thermal/thermal_zone0/temp
62000
root at letux:~# cat /sys/class/thermal/thermal_zone0/temp
63500
root at letux:~# cat /sys/class/thermal/thermal_zone0/temp
62000

There is a more or less systematic and immediate jump of +9°
for the second request. Maybe a bug in the hwmon readout?

All this is now done on an open GTA04A4 with external battery
and while not charging. Having battery charged and
case closed gives a different thermal profile of course.

One small observation: if I read the temp through the simple
"cat" command it stays constant while running the /root/temperature
script make it increase (but fall down quickly). This maybe
because the script does a lot of /sys scanning for the
real file name, i.e. leads to CPU activity.

BR,
Nikolaus