THe sudden appearance of "jc42"; sensord is clueless

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1

Asus TUF gaming b550-plus, amd ryzen 5 5600x, 32GB RAM

With kernel 6.11.0 the OS seems to have discovered a new temperature sensor: jc42. AFAICT it monitors the memory (DIMM) temperature. Sensord does not know it exists, yet the system journal is proudly displaying an ALARM for the sensor (see first log entry below).

The main sensor for the MB is nct6798. I have added it to sensord’s conf; some of the sensors are disabled (no meaningful reading) and not listed. What is not listed is jc42.

I have searched /etc/ and /usr/ for a jc42 configuration file, to no avail.

How do I configure jc42?

2024-09-28T11:50:17-07:00 sma-station14l sensord[11503]: Sensor alarm: Chip jc42-i2c-6-1b: temp1: 40.2 C (min = 0.0 C, max = 0.0 C) [ALARM]

2024-09-28T11:50:17-07:00 sma-station14l sensord[11503]: Chip: nct6798-isa-0290
2024-09-28T11:50:17-07:00 sma-station14l sensord[11503]: Adapter: ISA adapter
2024-09-28T11:50:17-07:00 sma-station14l sensord[11503]:   Vcore: +0.48 V (min = +0.00 V, max = +1.74 V)
2024-09-28T11:50:17-07:00 sma-station14l sensord[11503]:   in1: +1.01 V (min = +0.90 V, max = +1.10 V)
2024-09-28T11:50:17-07:00 sma-station14l sensord[11503]:   AVCC: +3.34 V (min = +2.98 V, max = +3.63 V)
2024-09-28T11:50:17-07:00 sma-station14l sensord[11503]:   +3.3V: +3.38 V (min = +2.98 V, max = +3.63 V)
2024-09-28T11:50:17-07:00 sma-station14l sensord[11503]:   in4: +1.02 V (min = +0.90 V, max = +1.10 V)
2024-09-28T11:50:17-07:00 sma-station14l sensord[11503]:   in5: +0.86 V (min = +0.80 V, max = +1.20 V)
2024-09-28T11:50:17-07:00 sma-station14l sensord[11503]:   in6: +0.26 V (min = +0.13 V, max = +0.38 V)
2024-09-28T11:50:17-07:00 sma-station14l sensord[11503]:   3VSB: +3.34 V (min = +2.98 V, max = +3.63 V)
2024-09-28T11:50:17-07:00 sma-station14l sensord[11503]:   Vbat: +3.31 V (min = +2.70 V, max = +3.63 V)
2024-09-28T11:50:17-07:00 sma-station14l sensord[11503]:   fan1: 0 RPM (min = 0 RPM)
2024-09-28T11:50:17-07:00 sma-station14l sensord[11503]:   fan2: 1344 RPM (min = 0 RPM)
2024-09-28T11:50:17-07:00 sma-station14l sensord[11503]:   fan3: 917 RPM (min = 0 RPM)
2024-09-28T11:50:17-07:00 sma-station14l sensord[11503]:   fan4: 898 RPM (min = 0 RPM)
2024-09-28T11:50:17-07:00 sma-station14l sensord[11503]:   fan5: 0 RPM (min = 0 RPM)
2024-09-28T11:50:17-07:00 sma-station14l sensord[11503]:   fan6: 0 RPM (min = 0 RPM)
2024-09-28T11:50:17-07:00 sma-station14l sensord[11503]:   fan7: 0 RPM (min = 0 RPM)
2024-09-28T11:50:17-07:00 sma-station14l sensord[11503]:   SYSTIN: 34.0 C (limit = 80.0 C, hysteresis = 75.0 C)
2024-09-28T11:50:17-07:00 sma-station14l sensord[11503]:   CPUTIN: 43.0 C (limit = 80.0 C, hysteresis = 75.0 C)
2024-09-28T11:50:17-07:00 sma-station14l sensord[11503]:   PECI Agent 0 Calibration: 43.0 C (limit = 80.0 C, hysteresis = 75.0 C)
2024-09-28T11:50:17-07:00 sma-station14l sensord[11503]:   TSI0_TEMP: 46.6 C
2024-09-28T11:50:17-07:00 sma-station14l sensord[11503]:   beep_enable: Sound alarm disabled
2024-09-28T11:50:17-07:00 sma-station14l sensord[11503]: Chip: amdgpu-pci-0900
2024-09-28T11:50:17-07:00 sma-station14l sensord[11503]: Adapter: PCI adapter
2024-09-28T11:50:17-07:00 sma-station14l sensord[11503]:   vddgfx: +1.08 V
2024-09-28T11:50:17-07:00 sma-station14l sensord[11503]:   fan1: 1041 RPM (min = 0 RPM)
2024-09-28T11:50:17-07:00 sma-station14l sensord[11503]:   edge: 46.0 C
2024-09-28T11:50:17-07:00 sma-station14l sensord[11503]: Chip: jc42-i2c-6-1b
2024-09-28T11:50:17-07:00 sma-station14l sensord[11503]: Adapter: SMBus PIIX4 adapter port 0 at 0b00
2024-09-28T11:50:17-07:00 sma-station14l sensord[11503]:   temp1: 40.2 C (min = 0.0 C, max = 0.0 C) [ALARM]
2024-09-28T11:50:17-07:00 sma-station14l sensord[11503]: Chip: k10temp-pci-00c3
2024-09-28T11:50:17-07:00 sma-station14l sensord[11503]: Adapter: PCI adapter
2024-09-28T11:50:17-07:00 sma-station14l sensord[11503]:   Tctl: 46.5 C
2024-09-28T11:50:17-07:00 sma-station14l sensord[11503]:   Tccd1: 48.5 C
2

https://docs.kernel.org/hwmon/jc42.html

I read that when the module is loaded lmsensors should see it.

What kind of configuration do want to do on it?

3

Checking the board it is DDR4 and AFAIK jc42 is for DDR3 only.

I checked my DDR4 DIMMs using:

> sudo zypper install i2c-tools
> decode-dimms

And it is reporting my DDR4 DIMMs have no temperature sensor.

decode-dimms | grep Thermal
Thermal Sensor                                   No
Thermal Sensor                                   No
Thermal Sensor                                   No
Thermal Sensor                                   No
4

The output you provided is from sensord which quite clearly shows that sensord knows (or at least believes) that is exists.

This ALARM comes from sensord. You are shooting the messenger.

Upload the full output of dmesg to the https://paste.opensuse.org/

5

You are correct. I did not see the entry in the sensor listing.

I want to set the min/max values. Both values are currently 0.0 C.

$ decode-dimms | grep -i thermal
67:Thermal Sensor   TSE2004 compliant
6

You are correct. I did not see it.

7

After a lot of searching, I created a configuration file for jc42.
So far the only command that works is label. No variation of temp1_* has made any difference in the default temperatures of 0.0C.

#  Chip: jc42-i2c-6-1b
#  Adapter: SMBus PIIX4 adapter port 0 at 0b00
#
chip "jc42-*"
    label "temp1" "DIMM Temp"

    set temp1_min      00
    set temp1_max      60
    set temp1_max_hyst 56

2024-09-30T12:34:36-07:00 sma-station14l sensord[148139]: Adapter: SMBus PIIX4 adapter port 0 at 0b00
2024-09-30T12:34:36-07:00 sma-station14l sensord[148139]:   DIMM Temp: 40.2 C (min = 0.0 C, max = 0.0 C) [ALARM]