Change in coreboot[master]: mb/google/dedede/var/magolor: Select touchscreen based on SSFC in FW_...

[Marco Chen (Code Review)]

Attention is currently required from: David Wu, Furquan Shaikh, Henry Sun, Karthik Ramasubramanian.
Marco Chen has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/52851 )

Change subject: mb/google/dedede/var/magolor: Select touchscreen based on SSFC in FW_CONFIG
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Patch Set 6:

(2 comments)

File src/mainboard/google/dedede/variants/magolor/overridetree.cb:

https://review.coreboot.org/c/coreboot/+/52851/comment/21598624_af1f952a 
PS5, Line 2: 	field CAMERA_WFC 38 40
> Different variants have different components and different sources. […]

* Definition of SSFC bits in coreboot per variant or baseboard is all fine to me so nothing we need to decide / change here.

* The real issue is that the same range of SSFC bits here is defined in coreboot for camera_wfc (variant level) but also is defined in EC (baseboard) for USB mux options. Therefore once in the future Magolor also needs to have multi-sources of USB mux then this same range of SSFC bits will be conflict between camera_wfc in coreboot and USB mux in EC.

File src/mainboard/google/dedede/variants/magolor/overridetree.cb:

https://review.coreboot.org/c/coreboot/+/52851/comment/a6a623a5_7544a83e 
PS6, Line 208: 10
> Can we not program the touch panel to use a different I2C address to solve this issue? […]

* partners mentioned that this panel is leveraged from other platform bound with touchscreen chip together so from supply management point of view, partners would like to keep them as the same part instead of configuring other slave address from FW level (vendor confirmed new slave address is set in FW level) which make them as two parts. As a result, it introduced the conflict in address here.

* Agree with you that options per touchscreen would be ideal and the reason of having this option is just because it is a compromised way to limit the options.

* Hi ODM team, could we change it to per touchscreen instead of panel size? And factory can still leverage EDID from panel to identify the touchscreen chip.