Cleaned up version of Edatec HMI drivers

[6by9]

My version of #7361 and #7362 actually using the various parts that I've requested.

I have no hardware to test it, but the behaviour should be the same.

I have not replicated the CM0 vs Pi4/CM4 timing difference for the 7" as I do not believe there needs to be one. It also avoids having to change the value for CMD_BRIDGE_INIT.

Patches need to be squashed/split appropriately before merge, hence draft.

@spp-bruk

[FrankLeeEDA]

Thank you for your careful review. We are adjusting the code and conducting testing based on your feedback. I noticed that you have replaced gpio_chip with gpio_degmap_config. Is this a better choice as the default defconfig does not enable CONFIG_GPIO_REGMAP.

[6by9]

I noticed that you have replaced gpio_chip with gpio_degmap_config. Is this a better choice as the default defconfig does not enable CONFIG_GPIO_REGMAP.

Modules should select their own dependencies via Kconfig rather than relying on the defconfig to include them.
You are right that I'd missed the select GPIO_REGMAP from the Kconfig entry for REGULATOR_EDATEC_10INCH, now added as an extra patch. It was already being built for me as our REGULATOR_RASPBERRYPI_TOUCHSCREEN_V2 module already selects it.

gpio_regmap_config removes all the boilerplate from the driver when a bank of N GPIOs are controlled via a simple register interface, and does allow for "missing" bits to be present in the register via the init_valid_mask hook. Define it with only reg_set_base and the GPIOs are output only, and only reg_dat_base makes it input only.

[FrankLeeEDA]

Ok, I understand. Our previous choice of gpio_chip was based on compatibility considerations. Prior to 6.18.y kernel merge here, our display driver was based on out-of-tree dynamic compilation and the official Raspberry OS doesn't include gpio_regmap. I will provide feedback on this modification to my colleague.

Another question is whether it is necessary to first use the drm/panel-simple patch #6by9@d69c6e4 before extracting the DSI porch parameter from panel-edatec-dsi driver to dtoverlay. However, I strongly agree with merging the 7inch panel driver and regulator into one driver file.

[FrankLeeEDA]

Also, a lot of redundant code from the original 10inch and 7inch driver had been deleted and we spend some time conducting tests. I will submit the driver update later today.