Created attachment 122692 [details]
dmesg output for the radeon driver
On a Lenovo G50-80 with Intel HD Graphics 5500 (Broadwell GT2) and Advanced
Micro Devices [AMD/ATI] Sun XT [Radeon HD 8670A/8670M/8690M / R5 M330] using
vgaswitcheroo with echo DDIS > /sys/kernel/debug/vgaswitcheroo/switch results
in a blank screen on logging out or in a message that client 0 refused to
switch and a reversion to the login screen (depending on the display manager in
use) on logging out and trying to log back in. The computer can be powered off
normally using the power button or the options in the login screen if visible
or by switching to a different VT. Trying to use the radeon driver with an XOrg
configuration file like the one attached results in the display manager not
starting (other VTs remain operational). The XOrg log (attached) shows that the
radeon driver fails to find a screen to its liking,
> (EE) RADEON(0): No modes.
> (EE) Screen(s) found, but none have a usable configuration.
and then gives up altogether:-
> (EE) no screens found(EE)
The message "radeon 0000:04:00.0: VCE init error (-22)." appears during boot;
the dmesg output for radeon is attached.
The problem occurs irrespective of whether the module parameter radeon.runpm =
0 or not.
The radeon configuration attached is adapted from the one used by Ubuntu 15.10
for fglrx. fglrx works properly on Ubuntu 15.10.