Querying PCI bus turns Nvidia on

Bumblebee-Project / bbswitch

Disable discrete graphics (currently nvidia only)

GNU General Public License v2.0

487 stars 78 forks source link

Querying PCI bus turns Nvidia on #175

Open haarp opened 6 years ago

haarp commented 6 years ago

Greetings.

I'm running kernel 4.14 on a Thinkpad W530. As soon as the PCI bus is queried, e.g. by lspci, the card instantly switches on. I do not remember if this had been an issue with earlier kernels.

The nvidia module remains untouched and unloaded throughout all this. The Bumblebee service also wasn't running.

> cat /proc/acpi/bbswitch 
0000:01:00.0 OFF
> lspci
....
....
> cat /proc/acpi/bbswitch 
0000:01:00.0 ON

Weird, isn't it?

haarp commented 6 years ago

It seems reading /sys/bus/pci/devices/0000:01:00.0/config (01:00.0 being the Nvidia) is what triggers the switch-on.

Lekensteyn commented 6 years ago

Yes, that is runtime PM that is becoming active. There is not much you can do about that other than setting pcie_port_pm=off, but then maybe it is better just to remove bbswitch. Related: https://github.com/Bumblebee-Project/Bumblebee/issues/978