I powered up my laptop. The kdm screen was there, but I did not log in. After
some time, perhaps 20-30 minutes, I was ready to log in. The screen was black,
but that occurs after idle, so no problem, just wiggle the mouse. Nothing
happened. The screen stayed black. I know the password field was focused, so I
typed it and the computer logged in. Still black screen. I typed ctrl-alt-f2 and
logged in as root. Still black screen. I typed reboot and the computer rebooted
and I again had a visible screen.
How can I wake up the display after it has gone into a sleep mode?