thinkpad_gsw

Toggles the ThinkPad PMH7's discrete graphics card power.

About half of the code is from bbswitch. I decided to rewrite the module with sysfs and add a few extra utilities.

Important

This uses undocumented tricks, use at your own risk. You may brick your system with this if you have no idea what you're doing!

Why this and not ACPI-based Optimus control?

Bit-banging the power management IC with x86 in/out ports is the only way I know of to toggle power to a Corebooted ThinkPad's GPU, as of 2024. This will probably change at a later time, once the ACPI Optimus control feature in Coreboot is complete.

Compatibility

• ThinkPad W541 (with Quadro K1100M or Quadro K2100M)

Installation

Use DKMS to install the driver.

Copy 10-dont-add-nouveau.conf to your Xorg config folder so that Xorg won't bind to your discrete graphics, making tpgsw_ctrl unable to switch off the discrete card.

To access tpgsw_ctrl easier, copy it to /usr/local/sbin/.

Usage

This utilizes Nouveau's DRI_PRIME=1 feature. For example:

$ sudo tpgsw_ctrl on
$ DRI_PRIME=1 glxgears -info
$ sudo tpgsw_ctrl off

Note the tpgsw_ctrl utility needs superuser privileges to run.