On 1/7/21 5:12 PM, Jiri Kosina wrote:

On Fri, 4 Dec 2020, Hui Wang wrote:

quoted

On the latest Thinkpad Yoga laptop, the touchscreen module is wacom
I2C WACF2200 (056a:5276), we found the touchscreen could not work
after rebooting, needs to poweroff the machine then poweron the
machine to let it work.

It is highly possible that this is a BIOS issue, but the windows
doesn't have this problem with the same BIOS.

If keeping the power on when calling shutdown, the touchscreen could
work after rebooting. Let us add a quirk for it and apply the quirk
to this machine only.

I wonder what do Windows do differently here. Perhaps they never put the
i2c device to sleep while in shutdown anyway? Is there any downside to
(not) doing the same?

It is highly possible the Windows doesn't sleep the i2c device in 
shutdown. When calling shutdown, it usually means reboot or poweroff the 
machine, so the sleep is meaningless in this situation. In other 
situations like users manually unload the i2c driver, maybe it will add 
a bit power consumption without sleeping the device.

Anyway, I will try to ask for help from vendor, maybe they could provide 
how Windows do when shutdown.

Thanks.

Thanks,