[M] Change in coreboot[master]: mb/google/link: rework TP/TS ACPI to add support for new Windows I2C ...

[Paul Menzel (Code Review)]

Attention is currently required from: CoolStar, Martin Roth, Matt DeVillier, Stefan Reinauer.

Paul Menzel has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/76159?usp=email )

Change subject: mb/google/link: rework TP/TS ACPI to add support for new Windows I2C driver
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Patch Set 5:

(2 comments)

Commit Message:

https://review.coreboot.org/c/coreboot/+/76159/comment/64c89d25_71fa800d :
PS5, Line 7: for new Windows I2C driver
Excuse my ignorance, but is that driver implemented in ACPI or do you also need to install a driver on Microsoft Windows?

https://review.coreboot.org/c/coreboot/+/76159/comment/45e3f902_fae13234 :
PS5, Line 9: This is a brand new I2C driver that is designed specifically for the Pixel 2013 chromebook (LINK). The GMBus interface on the IGPU is an i2c-compatible interface, but AFAIK only Link has touch devices attached in this way.
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           : On Windows, the PCIe device for the IGP is owned by the Intel proprietary driver, hence a separate ACPI device has to be added for the I2C driver arbitrator to attach to. The MMIO method is used instead of _CRS so that Windows does not try to assign ownership of the resource to our device (even though we're using the MMIO registers at the same time as the IGP driver).
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           : Even though in theory 2 drivers accessing the same MMIO may cause problems, in testing, there has been no issues with sleep/wake/hibernate, updating/installing/uninstalling the IGP driver, or changing display resolutions with the i2c driver attached.
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           : The arbitrator is necessary as well, since even though there are multiple i2c buses, the MMIO registers are shared. Hence a shared lock is required for i2c access across the buses.
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           : The original Sleep Button devices are preserved for Linux due to the completely custom and non-standard implementation of the Windows driver in order to work around the non-standard nature of Link's hardware.
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