RPI 7" display touch controller

[Tim Harvey]

On Thu, Nov 18, 2021 at 4:53 AM Marek Vasut <marex at denx.de> wrote:
>
> 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

Marek,

Thanks. This dt overlay actually disables the touchscreen controller
with a note that the IRQ must be hooked up to work. Did you actually
wire up an IRQ and get it to work? I implemented polling mode for the
controller but the data did not make sense.

This dt overlay also interests me as I am also wanting to get some
overlays in the kernel tree [1]. I'm curious if you have any thoughts
on why there are currently no overlays in the mainline tree.

1 - https://lore.kernel.org/linux-arm-kernel/20211115202426.16114-1-tharvey@gateworks.com/T/