powersaving-related hangs on T460s

[Meelis Roos <mroos@linux.ee>]

I tried 4.15-git on my Thinkpad T460s laptop. It is working but I have 
problems waking up the computer after it has been idle.

There should be no suspend (to keep network connections alive) when the 
laptop is on AC power, even when the lid is closed. In dmesg, I have 
seen no indication of suspend happening. It is configured to just lock 
the screen when the lid is closed.

Normally, I have to press a key after opening the lid to unblank the 
screen and get to password prompt. Usually this works but sometimes 
there is no response - power LED is on that is all, holding down power 
button is the only way out.

Sometimes it happens overnight, sometimes it is alive in the morning. It 
almost never happens with short 5-15 minutes breaks but it can happen 
for about hour long breaks. There is no reliable way to reproduce the 
problem.

4.14 with the same config (modulo any new config options) was working 
fine.

Nothing in the log files afterwards. Network connection is WiFi. There 
is a USB mouse connected.

Wat do I check next?

-- 
Meelis Roos (mroos@linux.ee)