Please add MCP9808 sensor support to i2c-sensor dtoverlay list

[Jibun-no-Kage]

Describe the bug

Not a bug but a support request. Please add MCP9808 sensor support to i2c-sensor dtoverlay list. As I understand it, this sensor already is supported by the Linux kernel? Thanks.

Steps to reproduce the behaviour

NA

Device (s)

Other

System

Latest Raspberry Pi firmware image (or so I believe what is how support is implemented).

Logs

No response

Additional context

Just a suggestion but maybe setup a sub section on github under the Raspberry Pi area for such requests?

[pelwell]

Done - see ac4cf1b.

GitHub doesn't allow the creation of arbitrary sections, and requesting additions via the Issues page works for us.

[Jibun-no-Kage]

Cool, I just did not want to post the requests the wrong way or such. I should be able to test MCP9808 sensor first thing tomorrow, once I get the update.

[Jibun-no-Kage]

Is this update published yet? Ran rpi-update on a Pi4, then added dtoverlay=i2c-sensor,mcp980x,addr=0x18 to /boot/config.txt, and rebooted, but did not see the typical UU on i2c-detect -y 1 scan? Shows 18 as address rather than UU.

[pelwell]

Not yet - the last update was on Monday. You can see the release history here: https://github.com/raspberrypi/rpi-firmware/commits/master

[Jibun-no-Kage]

Excellent, that is going to be a book mark! Thanks.

[popcornmix]

rpi-update contains this now.

[Jibun-no-Kage]

Excellent! Yup, now see kernel/dtoverlay control of the sensor, i.e. UU in i2c address slot (0x18) in the i2c detect result.

[Jibun-no-Kage]

Odd... the direct query of temp1_input under kernel/dtoverlay... the result is '62' which does not make sense. So I pulled the sample test script from Adafruit, and after loading the dependencies, and running the simple test, the results were as expected.

# cd /root
# apt install build-essential python3-dev python3-pip python3-smbus git
# pip3 install RPi.GPIO
# git clone https://github.com/adafruit/Adafruit_Python_MCP9808.git
# cd Adafruit_Python_MCP9808
# python3 setup.py install

# cd examples
# python3 simpletest.py
Temperature: 27.250C / 81.050F
Temperature: 27.312C / 81.162F
Temperature: 27.312C / 81.162F
Temperature: 27.250C / 81.050F

The dtoverlay just provides visibility to the native kernel support, right? Thus, I am not sure this is Raspberry Pi issue to solve, but documented here to illustrate there seems to be an issue with the existing kernel support for MCP9808 sensor.

[Jibun-no-Kage]

Ah, thanks! Look forward to testing.

[pelwell]

Oh dear. The mcp980x driver only supports the MCP980<x> family of devices when x is in the range 0-3. For MCP9804, MCP9805 and MCP9808 one needs the jc42 driver (obviously). Looking back at my commit I think the only thing wrong was the README comment, and the fact that it didn't solve your problem.

I'll add a jc42 option to the i2c-sensor overlay.

[pelwell]

41d7f47 is the update to the overlay. To save you waiting for the next build you can download a patched overlay here: https://drive.google.com/file/d/1eWeA3oRhVTrYI1Y57HLoXzy_dhXmQOd8/view?usp=share_link

Just sudo cp i2c-sensor.dtbo /boot/overlays/, edit config.txt to say dtoverlay=i2c-sensor,jc42 and reboot.

[Jibun-no-Kage]

Wow, I pulled the C source for the support of the MCP9808, but have not had time to review it as yet. Interesting.

First test is odd, after reboot...

# cat /sys/devices/platform/soc/fe804000.i2c/i2c-1/1-0018/hwmon/hwmon2/temp1_input
0
# i2cdetect -y 1
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: 08 09 0a 0b 0c 0d 0e 0f
10: 10 11 12 13 14 15 16 17 UU 19 1a 1b 1c 1d 1e 1f
20: 20 21 22 23 24 25 26 27 28 29 2a 2b 2c 2d 2e 2f
30: 30 31 32 33 34 35 36 37 38 39 3a 3b 3c 3d 3e 3f
40: 40 41 42 43 44 45 46 47 48 49 4a 4b 4c 4d 4e 4f
50: 50 51 52 53 54 55 56 57 58 59 5a 5b 5c 5d 5e 5f
60: 60 61 62 63 64 65 66 67 UU 69 6a 6b 6c 6d 6e 6f
70: 70 71 72 73 74 75 76 77

Look like the changes are flooding blasting the i2c bus?

I set boot/config.txt to...

dtoverlay=i2c-sensor,jc42
dtoverlay=i2c-sensor,mcp980x,addr=0x18

I pulled the VCC from the sensor, to reset it, and then got...

# i2cdetect -y 1
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- UU -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- UU -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --

Not sure where 0x68 is coming from, I only have 1 device on the i2c bus.

But still can seem to read the sensor right...

# cat /sys/devices/platform/soc/fe804000.i2c/i2c-1/1-0018/hwmon/hwmon2/temp1_input
62

Of course if I use the python script...

# python3 simpletest.py
Press Ctrl-C to quit.
Temperature: 28.000C / 82.400F
Temperature: 27.938C / 82.287F
Temperature: 28.000C / 82.400F

[Jibun-no-Kage]

Did one more reboot... And the phantom 0x68 is gone, and i2c detect scan clear...

# i2cdetect -y 1

     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:                         -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- UU -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --

But the sensor read is still not right...

# cat /sys/devices/platform/soc/fe804000.i2c/i2c-1/1-0018/hwmon/hwmon2/temp1_input
62

[pelwell]

You need to remove the usage of mcp980x - it's probably getting in the way.

[Jibun-no-Kage]

Testing now... just with the 'dtoverlay=i2c-sensor,jc42' or 'dtoverlay=i2c-sensor,jc42,addr=0x18' the typical UU is not present, just the raw address of 0x18. So, does not appear the kernel has control or access to the sensor.

# ls -l /sys/devices/platform/soc/fe804000.i2c/i2c-1/1-0018/
total 0
-r--r--r-- 1 root root 4096 Nov 7 17:30 modalias
-r--r--r-- 1 root root 4096 Nov 7 17:27 name
lrwxrwxrwx 1 root root 0 Nov 7 17:30 of_node -> ../../../../../../firmware/devicetree/base/soc/i2c@7e804000/jc42@18
drwxr-xr-x 2 root root 0 Nov 7 17:30 power
lrwxrwxrwx 1 root root 0 Nov 7 17:30 subsystem -> ../../../../../../bus/i2c
-rw-r--r-- 1 root root 4096 Nov 7 17:26 uevent
-r--r--r-- 1 root root 4096 Nov 7 17:30 waiting_for_supplier

There is not temp1_input file, so can't query for temperature via CLI. But, clearly the jc42 driver loaded...

# cat /sys/devices/platform/soc/fe804000.i2c/i2c-1/1-0018/name
jc-42.4-temp

What is interesting,is the mcp9808 is show as compatible.

Required properties:

• compatible: May include a device-specific string consisting of the
  manufacturer and the name of the chip. A list of supported
  chip names follows.
  Must include "jedec,jc-42.4-temp" for any Jedec JC-42.4
  compatible temperature sensor.

microchip,mcp9808

[Jibun-no-Kage]

But looking at the actual kernel patch for JEDEC? They don't list the MCP9808...
https://linux.kernel.narkive.com/fFuXz9Ak/patch-hwmon-add-support-for-jedec-jc-42-4-compliant-temperature-sensors

• • Microchip MCP9805, MCP98242, MCP98243, MCP9843
• Prefixes: 'mcp9805', 'mcp98242', 'mcp98243', 'mcp9843'
• Addresses scanned: I2C 0x18 - 0x1f

So I wonder if the actual kernel patch is missing what is otherwise documented? I only see references to the MCP9805.

The cool thing is the since you added the JEDEC compatibles that adds a lot of additional sensors to the pool. :) But we don't have the one i need working quite yet.

[Jibun-no-Kage]

I don't have a Pi setup to execute C source correctly, and I have little experience with C in Linux, versus on Macintosh and PC. If I can setup a C environment, but that would be the actual proof, to run the raw C code that the kernel has, right?

[pelwell]

https://github.com/raspberrypi/linux/blob/rpi-5.15.y/drivers/hwmon/jc42.c#L175

[Jibun-no-Kage]

Yup... { MCP_MANID, MCP9808_DEVID, MCP9808_DEVID_MASK }, That is good then, I am trying to brute force load the driver.

THAT WORKED!
https://www.kernel.org/doc/html/latest/hwmon/jc42.html

# modprobe jc42
# echo jc42 0x18 > /sys/bus/i2c/devices/i2c-1/new_device

# cat /sys/devices/platform/soc/fe804000.i2c/i2c-1/1-0018/hwmon/hwmon2/temp1_input
26562

So is what I did above not basically what the overlay is going to do?