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

[Karthik Ramasubramanian (Code Review)]

Attention is currently required from: David Wu, Furquan Shaikh, Henry Sun, Marco Chen.
Karthik Ramasubramanian 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/954795aa_8dbcb96b 
PS5, Line 2: 	field CAMERA_WFC 38 40
> I am afraid that the bit usage of SSFC is out of sync with EC side already. […]

Different variants have different components and different sources. Hence the scope of SSFC is preferred to be per-variant instead of baseboard. This also means we can keep bit allocations (offset and number of bits) in a per-variant manner.

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

https://review.coreboot.org/c/coreboot/+/52851/comment/79a042c3_63491beb 
PS6, Line 208: 10
Can we not program the touch panel to use a different I2C address to solve this issue?

Except for the hardware ID, the entire power sequencing for this 14" panel and ELAN6915 11" panel are identical.

The way SSFC is used in this CL is not how it meant to be used. Also we would have already released devices with panel size unprovisioned. This change is going to break the touch panel in those unprovisioned devices.

If SSFC still needs to be used, I would prefer to allocate a unique ID for each touchpanel and probe them in the devicetree i.e.

fw_config TS_SOURCE 41 44
    option TS_UNPROVISIONED 0
    option TS_ELAN_6915 1
    option TS_ELAN_6918 2
    option TS_ELAN_0001 3
    option TS_RAYD_0001 4
end