[S] Change in coreboot[master]: mb/google/skyrim: Implement touchscreen power sequencing

[Matt DeVillier (Code Review)]

Attention is currently required from: Raul Rangel, Jason Nien, Martin Roth, Karthik Ramasubramanian.

Matt DeVillier has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/67778 )

Change subject: mb/google/skyrim: Implement touchscreen power sequencing
......................................................................

Patch Set 4:

(1 comment)

File src/mainboard/google/skyrim/variants/baseboard/gpio.c:

https://review.coreboot.org/c/coreboot/+/67778/comment/8db59771_7df2937e 
PS3, Line 116: 	/* EN_PP3300_TCHSCR */
             : 	PAD_GPO(GPIO_131, LOW),
             : 	/* TCHSCR_RESET_L */
             : 	PAD_GPO(GPIO_136, LOW),
> When all the touchscreen modules defined in devicetree could not be probed, we can put these GPIOs as NC?

I've thought about that, but not come up with a good idea on how to determine at runtime (which would be necessary for older/existing boards for which we can't backport using FW_CONFIG). My least-worst idea is to create a new i2c touchscreen device driver which contains one or more generic i2c or i2c-hid devices, and could keep track if any present / turn off the GPIOs if none found. But still seems suboptimal to me