Tested with drivers from NVIDIA (nvidia module). Driver version needs to be >=304.137
for the i2c ports found on board (or on monitors connected to the board) to be exposed.
Not tested with nouveau but this should also expose the i2c ports found on the board.
This is what lspci -v gives me:
07:00.3 Serial bus controller [0c80]: NVIDIA Corporation TU104 USB Type-C UCSI Controller (rev a1)
Subsystem: ASUSTeK Computer Inc. TU104 USB Type-C UCSI Controller
Flags: bus master, fast devsel, latency 0, IRQ 5
Memory at f6084000 (32-bit, non-prefetchable) [size=4K]
Capabilities: [68] MSI: Enable- Count=1/1 Maskable- 64bit+
Capabilities: [78] Express Endpoint, MSI 00
Capabilities: [b4] Power Management version 3
Capabilities: [100] Advanced Error Reporting
First, install requirements:
apt install i2c-tools nvidia-smi
modprobe i2c-dev
Then cd into asus_fc2_userland. Check out which i2c adapter to use, for example here: "2".
Set fan at full speed, to make sure everything is alright. (Change 0xFF for a lower value for lower speeds.)
i2cset 2 0x2a 0x41 0xFF
Edit the monitoring script asus_fc2.sh to your make sure everything is set up properly, and install the monitoring script & systemd service:
sudo make install
And that's it!
If you want to log every PWM value being set, edit /etc/systemd/system/asus_fc2.service and change:
ExecStart=/bin/bash /usr/local/bin/asus_fc2.sh -l
to
ExecStart=/bin/bash /usr/local/bin/asus_fc2.sh
Figure out your i2c device.
cd asus_fc2
make
sudo make install
modprobe asus_fc2
I2C_DEVICE_ADDRESS="0x2a" # << might be different if using a different Asus board than mine
I2C_BUS="2" # << might be different on your machine. Use i2cdetect method above to find it
echo asus_fc2 "${I2C_DEVICE_ADDRESS}" > /sys/bus/i2c/devices/i2c-${I2C_BUS}/new_device>
And now you should have a new hwmon device you can use.
# for hwmon in /sys/class/hwmon/hwmon*; do if [[ "asus_fc2" == $(cat "${hwmon}/name") ]]; then echo $hwmon ; fi; done
/sys/class/hwmon/hwmon2
# echo 255 > /sys/class/hwmon/hwmon2/pwm1
And hear your fan SPIN !
Unfortunately, I couldn't find a way to report the GPU temperature by reading on this i2c device. I actually couldn't even
find a way to get this information from the kernel space. nouveau driver is doing some weird voodoo shit
to access it and export on their own module.
This means unfortunately, we can't use fancontrol to manage the fan speed to cool down our GPU....
For this to work we need to path the nvidia driver (might not be needed with nouveau).
I have it installed with dkms.
Patch it with the following (see Notes below as to why).
# diff -u /tmp/nv-i2c.c /usr/src/nvidia-current-440.82/nvidia/nv-i2c.c
--- /tmp/nv-i2c.c 2020-04-15 23:59:55.488972454 +0200
+++ /usr/src/nvidia-current-440.82/nvidia/nv-i2c.c 2020-04-15 23:08:36.386176825 +0200
@@ -196,6 +196,7 @@
struct i2c_adapter nv_i2c_adapter_prototype = {
.owner = THIS_MODULE,
+ .class = I2C_CLASS_HWMON,
.algo = &nv_i2c_algo,
.algo_data = NULL,
};
Now rebuild your driver, and probably also reboot
dkms remove -m nvidia-current -v 440.82 -k all
dkms build -m nvidia-current -v 440.82 -k all
dkms install nvidia
reboot
And now that your nvidia i2c adapter is not a little bitch anymore, you can just do:
cd asus_fc2_module
make
sudo make install
modprobe asus_fc2
for hwmon in /sys/class/hwmon/hwmon*; do if [[ "asus_fc2" == $(cat "${hwmon}/name") ]]; then echo $hwmon ; fi; done
echo 255 > /sys/class/hwmon/hwmon2/pwm1
You'll probably have to re-do this everytime the nvidia drivers get updated.
I couldn't get autodetection to work, after implementing the i2c_driver->detect() function, it would actually not be called.
The documentation is not super clear as to what is going on:
Only buses which are likely to have a supported device and agree to be probed, will be probed. For example this avoids probing for hardware monitoring chips on a TV adapter.
So how can an i2c adapter decide not to be probed?
Detection should happen in function i2c_detect_address in drivers/i2c/i2c-core-base.c, which is it self called by i2c_detect().
There are a bunch of dev_dbg() calls that might help us make sure we hit these functions. To enable their output to dmesg we need to enable Dynamic debug.
# enable all messages from file i2c-core.c
echo 'file drivers/i2c/i2c-core.c +p' > /sys/kernel/debug/dynamic_debug/control
With asus_fc2.ko built & installed with:
make && sudo make install
we see the following messages
Apr 15 00:02:55 pc kernel: [ 4372.671967] i2c-core: driver [asus_fc2] registered
Apr 15 00:02:55 pc kernel: [ 4372.671972] i2c i2c-0: found normal entry for adapter 0, addr 0x2a
Apr 15 00:02:55 pc kernel: [ 4372.672522] i2c i2c-1: found normal entry for adapter 1, addr 0x2a
But what about the other i2c busses? It turns out the nvidia-backed i2c adapter we want to talk to has id 2.
It looks like what prevents us from reaching the proper detection line is the following code:
/* Stop here if the classes do not match */
if (!(adapter->class & driver->class))
return 0;
While I suppose driver->class here is the one define in the i2c_driver struct (.class = I2C_CLASS_HWMON), but I couldn't find how to display the reported adapter class. Nothing shows up in relevant places in /sys.
I basically want MORE dev_dbg and see what's in the i2c_adapter struct in i2c_detect(). We have multiple solutions
- Add the calls to
dev_dbg()ini2c-core.c, recompile the kernel, reboot. - Use one of the recent live kernel patching methods like kpatch to change the code.
- Use bpftrace to hook that method and display its arguments.
Since I hate anything new, and change is terrible, I first tried solution 1. While the thing was compiling (it still takes, like 3 mins on my new machine! :3) I also looked at solution 2.
I couldn't make it work, and while complaining about how everything was terrible on IRC someone told me about eBPF and bpftrace.
It's actually quite simple to use once you figure out what you need to do.
First figure out if your function is traceable:
# bpftrace -l | grep i2c_detect
kprobe:i2c_detect
And write the small program that will take the first arg of i2c_detect and log the value of class for it:
$ cat i2c.bt
#include <linux/i2c.h>
#include <linux/i2c-smbus.h>
kprobe:i2c_detect
{
$adapter = (struct i2c_adapter *)arg0;
$driver = (struct i2c_driver *)arg1;
printf("I2C adapter: %s \n", $adapter->name);
printf("adapter class: %d, driver class: %d\n", $adapter->class, $driver->class);
}
Run bpftrace:
# bpftrace i2c.bt
Attaching 1 probe...
I2C adapter: SMBus PIIX4 adapter port 0 at 0b00
adapter class: 129, driver class: 1
I2C adapter: SMBus PIIX4 adapter port 2 at 0b00
adapter class: 129, driver class: 1
I2C adapter: NVIDIA i2c adapter 1 at 7:00.0
adapter class: 0, driver class: 1
I2C adapter: NVIDIA i2c adapter 3 at 7:00.0
adapter class: 0, driver class: 1
I2C adapter: NVIDIA i2c adapter 5 at 7:00.0
adapter class: 0, driver class: 1
I2C adapter: NVIDIA i2c adapter 6 at 7:00.0
adapter class: 0, driver class: 1
I2C adapter: NVIDIA i2c adapter 7 at 7:00.0
adapter class: 0, driver class: 1
I2C adapter: NVIDIA i2c adapter 8 at 7:00.0
adapter class: 0, driver class: 1
Ah ha ! So our nvidia i2c adapter is not declaring anyclass, which makes the test fail in i2c_detect, and the adapter to be ignored.
And indeed, in /usr/src/nvidia-current-440.82/nvidia/nv-i2c.c (installed via nvidia-kernel-dkms package), their i2c_adapter struct is instantiated without specifying the class:
struct i2c_adapter nv_i2c_adapter_prototype = {
.owner = THIS_MODULE,
.algo = &nv_i2c_algo,
.algo_data = NULL,
};
So you can patch it
struct i2c_adapter nv_i2c_adapter_prototype = {
.owner = THIS_MODULE,
.class = I2C_CLASS_HWMON | I2C_CLASS_DDC, # Probably just need I2C_CLASS_HWMON
.algo = &nv_i2c_algo,
.algo_data = NULL,
};
Rebuild your module, and voila! Magic autodetection with a simple modprobe
This can be done in a Ubuntu LiveCD. Remember to have i2c-dev module running:
apt install i2c-tools
modprobe i2c-dev
Then provide the output of:
# for bus in $(i2cdetect -l | grep NVIDIA | cut -d$'\t' -f 1 | cut -d "-" -f 2); do echo "i2c bus: $bus"; i2cdetect -y $bus; done
Try to figure out which i2c device to use. We're looking for address 0x2a (which is from an ASUS ROG Strix 2070S):
# for bus in $(i2cdetect -l | grep NVIDIA | cut -d$'\t' -f 1 | cut -d "-" -f 2); do echo "i2c bus: $bus"; i2cdetect -y $bus| grep -B4 " 2a "; done
i2c bus: 3
i2c bus: 6
i2c bus: 4
i2c bus: 2
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: -- -- -- -- -- 08 -- -- -- -- -- -- --
10: -- -- -- -- -- 15 -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- 27 -- -- 2a -- -- -- -- --
i2c bus: 7
i2c bus: 5
This means the i2c bus is number 2.
# i2cdump 2 0x2a
No size specified (using byte-data access)
WARNING! This program can confuse your I2C bus, cause data loss and worse!
I will probe file /dev/i2c-2, address 0x2a, mode byte
Continue? [Y/n]
0 1 2 3 4 5 6 7 8 9 a b c d e f 0123456789abcdef
00: 00 00 00 00 00 00 00 01 00 01 00 83 00 00 00 00 .......?.?.?....
10: 00 00 00 00 00 35 00 00 00 00 00 00 00 00 08 01 .....5........??
20: 15 89 00 00 00 80 ff 32 3c 50 3c 46 50 03 00 ff ??...?.2<P<FP?..
30: 00 00 02 00 00 00 00 00 00 00 00 00 00 cc 02 00 ..?..........??.
40: 02 8d 00 00 2f 01 00 00 30 01 00 00 00 00 00 00 ??../?..0?......
50: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
60: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
70: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
90: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
a0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
c0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
d0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
same with 0x68