Missing Plasma sensors wih linux-raspberrypi4

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Missing Plasma sensors wih linux-raspberrypi4

Postby snack » Sun Sep 26, 2021 5:56 pm

I set up a Plasma desktop on an ArchLinux ARM installation on a Raspberry Pi 4 using the linux-aarch64 kernel. Everything worked fine, and I ws able to set up system monitor widgets for various sensors (CPU usage and temperature, memory usage). I then replace the kernel with linux-raspberrypi4, and after rebooting no sensors are available for the widgets, which now display nothing. I don't know what's the issue (maybe the rpi4 kernel lacks support for hardware sensors?); the only additional information that in my opinion might be relevant is that pacman removed the uboot-raspberrypi package when I installed linux-raspberrypi4 kernel, but I don't know if this is significant.
Any help is greatly appreciated, thanks.
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Re: Missing Plasma sensors wih linux-raspberrypi4

Postby graysky » Sun Sep 26, 2021 6:06 pm

Perhaps differences in where the kernels map sensors? Did you re-run sensors-detect on the new kernel package?
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Re: Missing Plasma sensors wih linux-raspberrypi4

Postby snack » Sun Sep 26, 2021 6:12 pm

No, I did not run sensors-detect, just installed the linux-raspberrypi4 package. I just run sensors-detect and it reported "Sorry, no sensors detected". I'm going to revert to linux-aarch64 to see if this helps.
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Re: Missing Plasma sensors wih linux-raspberrypi4

Postby snack » Sun Sep 26, 2021 6:49 pm

I reinstalled linux-aarch64 and the sensors are back. Then I went back on linux-raspberrypi4 and the sensors vanished again. so I'd say that it's really a problem with linux-raspberrypi4, although I don;t know what it could be since I'm not a kernel expert.
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Re: Missing Plasma sensors wih linux-raspberrypi4

Postby graysky » Mon Sep 27, 2021 12:16 am

On the rpi4 kernel, I get the core temp via:
$this->bbcode_second_pass_code('', '!/bin/sh
temp=$(cat /sys/devices/virtual/thermal/thermal_zone0/temp)
freq=$(sleep 0.1s && cat /sys/devices/system/cpu/cpufreq/policy0/scaling_cur_freq)
gov=$(cat /sys/devices/system/cpu/cpufreq/policy0/scaling_governor)
vcore=$(vcgencmd measure_volts core | awk -F"=" '{ print $2 }')

echo "CPU temp : $(( temp / 1000 ))°C"
echo "CPU freq : $(bc <<< "scale=0; $freq/1000") MHz @ $vcore ($gov)"
echo "Thermal brake : $(vcgencmd get_throttled)"
echo "Processor : $(grep -m1 'model name' /proc/cpuinfo | sed 's/^.*: //')"
')
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Re: Missing Plasma sensors wih linux-raspberrypi4

Postby snack » Mon Sep 27, 2021 6:20 am

Yes, those commands work also for me, but Plasma system monitor widgets are still broken. In journalctl I found that the plasma-ksystemstats unit fails to start:
$this->bbcode_second_pass_code('', '
Sep 27 08:04:04 tv systemd[385]: Starting Track hardware statistics...
Sep 27 08:05:34 tv systemd[385]: plasma-ksystemstats.service: start operation timed out. Terminating.
Sep 27 08:05:34 tv systemd[385]: plasma-ksystemstats.service: Failed with result 'timeout'.
Sep 27 08:05:34 tv systemd[385]: Failed to start Track hardware statitics.
')
which does not fail when using linux-aarch64, so I guess it's the culprit. The unit is activated via dbus at Plasma startup, and the /usr/bin/ksystemstats executable does not start even manually: it hangs forever without any debug printout, so I don't know how to debug it.
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Re: Missing Plasma sensors wih linux-raspberrypi4

Postby graysky » Mon Sep 27, 2021 9:48 am

What is the output of sensors under both kernels? For example, under rpi4:
$this->bbcode_second_pass_code('', '% sensors
cpu_thermal-virtual-0
Adapter: Virtual device
temp1: +53.1°C

rpi_volt-isa-0000
Adapter: ISA adapter
in0: N/A
')
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Re: Missing Plasma sensors wih linux-raspberrypi4

Postby snack » Mon Sep 27, 2021 2:57 pm

For both kernels I obtain the same output you posted, except an additional temperature detail with aarch64:
$this->bbcode_second_pass_code('', '
temp1: +57.9 C (crit = +90.0 C)
')
i.e. the critical value which is absent with rpi4 kernel.
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