Created attachment 1143301 [details] dmesg output for the radeon driver Description of problem: 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. Version-Release number of selected component (if applicable): 7.6.1-3.20160215gitd41fccc I have reported this upstream.
Created attachment 1143302 [details] Sample XOrg configuration for the radeon driver
Created attachment 1143303 [details] XOrg log for the radeon driver
From what I've read in comments upstream, apparently the radeon driver does not automatically offload the discrete GPU's content to the integrated GPU's buffer on systems with offloading GPUs that aren't connected to a display unit directly (where the discrete GPU's content is copied to the integrated one's buffer and then rendered by the latter). The GPU can be activated by setting the DRI_PRIME environment value to 1 for the program that needs to be run via the discrete GPU. So this works in a way, but is inconvenient if we want to run the entire session through the discrete GPU (I'm guessing that we would have to run the display manager itself, GDM, LightDM, etc., using DRI_PRIME). Being able to automatically select the GPU, e.g., the way fglrx does on (pre-16.04) Ubuntu using an XOrg configuration file, would be helpful.
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