R7800 thermal sensors... which physical part of the hardware these correspond to?

For Developers
1

I see there are 4 thermal sensors the current LEDE build is able to read:
/sys/devices/virtual/thermal/thermal_zone$i/temp

Does anyone know how these 4 map back to the physical hardware of the R7800? I am making an assumption that 2 of them would be for the two radios and the other 2 might be for CPU and memory or CPU core0 and core1.

On experiment I tried was to stress the CPU and see if 2 of the readings got notably higher than the others but it seems that they all increased. After 20 min of cpu stress, I get elevated temps across the board (between 7 and 13 degrees).

If I measure them with the governor set to 'performance' with no load and both radios off:

# cut -c1-2 /sys/devices/virtual/thermal/thermal_zone*/temp
46
45
46
41

And then if I run stress and let it sit for 20 min:

# stress -v -c 2
stress: info: [12346] dispatching hogs: 2 cpu, 0 io, 0 vm, 0 hdd
stress: dbug: [12346] using backoff sleep of 6000us
stress: dbug: [12346] --> hogcpu worker 2 [12347] forked
stress: dbug: [12346] using backoff sleep of 3000us
stress: dbug: [12346] --> hogcpu worker 1 [12348] forked

<<< physically sit and wait for 20 min >>>

# cut -c1-2 /sys/devices/virtual/thermal/thermal_zone*/temp
53
52
59
52

So after 20 min of stress:
temp0 +7
temp1 +7
temp2 +13
temp3 +11

Now I stopped stress (ctrl+c) and after 10 seconds:

# cut -c1-2 /sys/devices/virtual/thermal/thermal_zone*/temp
50
48
50
43

Temps now:
temp0 +4
temp1 +4
temp2 +3
temp3 +2

I don't know what conclusions if any we can draw from these data. All sensors are near by the CPU? Temp2 and temp3 are physically near each other?

2

I think that they are all from the CPU/chipset (8065), not from the WLAN.

Discussions from 2016 in e.g. these threads / pull requests:
Supporting thermal sensors on ipq806x
https://github.com/lede-project/source/pull/533

(the chipset actually/supposedly supports 11 sensors in 8065. All eleven sensors were visible in the testing phase a year ago, but most of those are some kind of duplicates)

1 Like
3

Thanks for the reply and for the links. Pity there aren't tech. specs. out there somewhere (at least not that I could find via googling).

4

It is still a bit unclear, as the chipset manufactureer has not provided detailed descriptions.

I think that the 17.01 branch may have only four sensors available, but master has 11 since this commit in early 2017:
https://git.lede-project.org/?p=source.git;a=commitdiff;h=dc32d0a53cc01d9f644c6e9851b6770440d4b28c

"tsens driver"
https://git.lede-project.org/?p=source.git;a=history;f=target/linux/ipq806x/files-4.9/arch/arm/boot/dts/qcom-ipq8064.dtsi;h=9996bd74151a3db1d9516a178e07e6470b134373;hb=HEAD

The earlier implementation, still there in 17.01:
https://git.lede-project.org/?p=source.git;a=commitdiff;h=fef6a96d9e9e001a28b6a673c56ed79029457b5d

2 Likes
5

I am not daring enough to attempt compiling and flashing the resulting image :slight_smile: I will rely on you experts for that. As an aside, thank you for all the development work and time you guys put into LEDE. It is a great distro.