RPI 7" display touch controller

[Tim Harvey]

Greetings,

I'm trying to get a RPI 7" touchscreen display working on an IMX8MM
board and while I've been able to get the MIPI DSI display and
backlight working I still can't seem to figure out the touch
controller.

It's supposed to have an FT5406 controller on it without an interrupt
so I added polling support drivers/input/touchscreen/edt-ft5x06.c
which I was able to verify using another touchscreen with that
controller but when reading data from the FT5406 on the RPI controller
the data does not make sense.

These panels appear to route the I2C from the FT5406 to a STM32F103
MPU that then provides a different I2C slave interface to the 15pin
connector that I'm connected to. On that I2C interface I see an i2c
slave at 0x45 which is managed by the regulator driver Marek wrote
(drivers/regulator/rpi-panel-attiny-regulator.c) and there is also an
i2c slave at 0x38 which I assumed was the FT5406 but I believe the MPU
is perhaps obfuscating that touch data.

Anyone have any ideas on how to make that touch controller useful?

Best regards,

Tim