in /etc/X11/xorg.conf, change:
Section "Device" Identifier "Configured Video Device" Driver "intel" EndSection
to
Section "Device" Identifier "Configured Video Device" Driver "intel" Option "ForceEnablePipeA" "true" EndSection
in /etc/X11/xorg.conf, change:
Section "Device"
Identifier "Configured Video Device"
Driver "intel"
EndSection
to
Section "Device"
Identifier "Configured Video Device"
Driver "intel"
Option "ForceEnablePipeA" "true"
EndSection