[Bug 215003] apple_gmux fails to initialize and iGPU unclaimed on MacBook Pro 16" 2019

[bugzilla-daemon@bugzilla.kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=215003

Lukas Wunner (lukas@wunner.de) changed:

           What    |Removed                     |Added
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                 CC|                            |lukas@wunner.de

--- Comment #2 from Lukas Wunner (lukas@wunner.de) ---
vga_switcheroo_client_probe_defer() only returns true if invoked by the
*inactive* GPU's driver. (That's the "pdev != vga_default_device()" condition.)
In other words, you've enabled the iGPU but it's not the *active* one. You need
to use the gpu-switch utility (https://github.com/0xbb/gpu-switch) to tell the
EFI BIOS that it should switch to the iGPU on next boot. That should resolve
the issue.

Unfortunately we don't support GPU switching for retina MBPs in the kernel yet,
hence have to rely on the EFI BIOS to do that for now. (We do support GPU
switching for *pre-retina* MBPs in the kernel since early 2016.)

However, I'd like to know why apple_gmux fails to probe with "Failed to find
gmux I/O resource". Could you attach an ACPI dump to this bugzilla? Thanks!

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