On Tue, Aug 30, 2016 at 11:25 AM, Roland Singer roland.singer@desertbit.com wrote:
I tried these scenarios:
Booted the system without the bbswitch module. The nouveau module was loaded and is responsible for the power management of the GPU. The graphical session freezes after some minutes...
Booted the system without bbswitch and with nouveau blacklisted. Manually loaded bbswitch to switch off the discrete GPU. Same freeze after a while or by explicitly obtaining the GPU state.
Is there a possibility to switch off the discrete card without bbswitch? If this is possible, then I could test this without nouveau and bbswitch at all. If the system hangs, then it is not the video driver nor bbswitch.
You can use acpi_call (a random search points to https://github.com/mkottman/acpi_call, but I don't know if that's the "official" version) - need to find the right method to call, but that's basically all it takes to acpi-suspend a gpu.
Separately, there was a recent fix to ... something, including but not limited to nouveau, involving hangs on gpu suspend on newer laptops. I don't think it's upstream yet. Look for patches from Lukas Wunner.
-ilia