RPI 7" display touch controller

[Marek Vasut]

On 11/18/21 2:25 AM, Tim Harvey wrote:
> 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?

Look around:
https://github.com/dh-electronics/meta-dhsom-stm32-bsp/blob/dunfell-3.1/recipes-kernel/linux/linux-stable/5.10/dh-stm32mp1-dhsom/0038-ARM-dts-stm32-Add-AV96-DTO-for-DH-644-100-DSI-mezzan.patch