Some issues with coreboot on T420 (touchpad and phone jack)
Synaptics Touchpad and Trackpint driver doesnot work originally under Windows 10 (but work under linux). The reason is the ACPI\VEN_PNP&DEV_0F13 generated by the coreboot can not be recognized by the driver. To workaround this, uncomment this line (MS_GROUP01_InterTouch_Inst,*PNP0F13) in the SynPD.inf file of Synaptics offcial driver. The PNP0F13 is probably adopted from previous models but no longer the name for T420. Is it possible to replace it with a right one?
The phone jack does not produce sound in Windows 10. It works fine under linux.
Throttling not work natively. On linux we have to install thermald to prevent overheating. But there seems not an equivalent software under Windows.