Ubuntu: Use vga switcheroo on MacBook Pro 8,2?



Question:

I have used the instructions provided by tomodachi here to get EFI kernel stub booting working properly. The Radeon card is now properly initialized and lspci is showing both graphics cards, which is appropriate.

However, I can't seem to use vga switcheroo properly. The problem seems to be modprobe.blacklist=i915. Booting with precisely the options laid out in the answer there:

modprobe.blacklist=i915 radeon.modeset=1

seems to disable vga switcheroo, as when I search for the switch file, it tells me /sys/kernel/debug/vgaswitcheroo is not a directory.

However, while in Ubuntu, if I run:

modprobe i915

vgaswitcheroo appears, but I get a weird screen-within-a-screen (the Radeon driver's environment remains, and the i915 driver draws a slightly smaller second screen in the upper left hand corner almost like a windowless virtual machine) and running

echo OFF > /sys/kernel/debug/vgaswitcheroo/switch

has no apparent effect. The system also disallows me from doing either:

modprobe -r radeon

or

modprobe -r i915

because it says both modules are in use.

I've tried booting with just modeset=1 (no radeon.modeset or modprobe.blacklist) and the result is that same screen-within-a-screen.

Running:

modprobe.blacklist=radeon i915.modeset=1

causes the system to boot into low graphics mode.

Any insights on this? Tomodachi's answer said "I got vga switcheroo working" but I'm not able to contact him directly due to lack of reputation.


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