Ps thanks for the info about the regulator, was a bit confused for a sec on that one but makes sense.The regulator controller at address 0x45 should respond to "i2cdetect -y 0" if the display is connected to DISP0, and "i2cdetect -y 10" when connected to DISP1.
If using DISP0, the correct line is "dtoverlay=vc4-kms-dsi-7inch,dsi0" - I've just created a PR for the documentation as it was wrong.
If using DISP1, the correct line is "dtoverlay=vc4-kms-dsi-7inch".
The touch controller on address 0x38 will only respond if the regulator has been requested to supply power to it, and that will require both the regulator and touch controller drivers to have been loaded.
i2c-10 is also used by the fan controller.
I have had it happen that shorting the tacho and power pins on the fan connector blows up the fan controller IC such that it pulls the I2C bus constantly low. Physically removing the chip from the CM4IO board was the only route to getting the bus working again.
Further debugging will need full kernel logs.
Statistics: Posted by forbiddenera — Wed Aug 27, 2025 4:51 pm
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