[Bug 88861] [efi, i915, vgaswitcheroo, black screen, nouveau] Screen goes black when switching from dedicated nvidia graphics card (nouveau) to integrated

[bugzilla-daemon at bugzilla.kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=88861

Paul Hordiienko <pvt.gord at gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|high                        |low

--- Comment #3 from Paul Hordiienko <pvt.gord at gmail.com> ---
Just realised that switching works if force integrated card load first.
In this case there is just one issue with uncorrect resolution in console when
switched on discrete card. For fix it helps patch from Darkulix:
https://github.com/ah-/gmux-scripts/issues/1#issuecomment-53850868

Steps:

1) Patch kernel and install it
2) Boot Linux kernel
3) Turn on nvidia card using: 

   echo ON > /sys/kernel/debug/vgaswitcheroo/switch; rmmod nouveau; echo DIS >
/sys/kernel/debug/apple_gmux/switch; modprobe nouveau; echo DIS >
/sys/kernel/debug/vgaswitcheroo

4) Switch to intel card: 

   echo IGD > /sys/kernel/debug/apple_gmux/switch; echo IGD >
/sys/kernel/debug/vgaswitcheroo/switch"

5) Now resolution will be correct in both cases

6) For further switching it is possible to use just:

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

and

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

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