[Bug 117131] vga_switcheroo does not switch IGP -> DIS ( IGP == i915 , DIS == radeon )

bugzilla-daemon at bugzilla.kernel.org bugzilla-daemon at bugzilla.kernel.org
Mon Apr 25 17:49:31 UTC 2016


https://bugzilla.kernel.org/show_bug.cgi?id=117131

--- Comment #8 from Jason Vas Dias <jason.vas.dias at gmail.com> ---
As stated on the web-page quoted above , 
( https://wiki.archlinux.org/index.php/PRIME )
an example xorg.conf to use the discrete card
as primary GPU is:


# Discrete Card as Primary GPU

Section "ServerLayout"
    Identifier "layout"
    Screen 0 "nouveau"
    Inactive "intel"
EndSection

Section "Device"
    Identifier  "nouveau"
    Driver      "nouveau"
    BusID       "PCI:x:x:x" # Sample: "PCI:1:0:0"
EndSection

Section "Screen"
    Identifier "nouveau"
    Device "nouveau"
EndSection

Section "Device"
    Identifier  "intel"
    Driver      "intel"
    BusID       "PCI:x:x:x"  # Sample: "PCI:0:2:0"
EndSection

Section "Screen"
    Identifier "intel"
    Device "intel"
EndSection




My xorg.conf is basically the same with the string 'nouveau' 
replaced by 'ati' .

It started out as simple as this, but then grew as I tried 
every conceivable method to specify the modes ,  but still
the X-server exits with a 'No modes.' error in every case .

The reason the X-server cannot determine the modes is because
of this Linux bug - the radeon DRM driver makes incorrect ACPI
calls.

Also I think that if vga_switcheroo does not work or is 
incapable of working , as it provably is in the above 
example, it should return EIO on the write to the 
debugfs control 'switch' file , and not proceed to
display spurious data in that file.

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