Distro: SLED11-SP1 Kernel: 2.6.39-rc3 Reproduce step: CASE A: The internal LVDS output will become blank $ xrandr --output LVDS1 --mode <COMMON RESOLUTION> --output VGA1 --off $ xrandr --output VGA1 --mode <COMMON RESOLUTION> --output LVDS1 --off $ xrandr --output LVDS1 --mode <COMMON RESOLUTION> --output VGA1 --off CASE B: The external VGA output will become blank $ xrandr --output VGA1 --mode <COMMON RESOLUTION> --output LVDS1 --off $ xrandr --output LVDS1 --mode <COMMON RESOLUTION> --output VGA1 --off $ xrandr --output VGA1 --mode <COMMON RESOLUTION> --output LVDS1 --off The <COMMON RESOLUTION> is any one of the common resolutions of internal LVDS and external VGA monitor. If you use different resolution, the issue will not be able to reproduce. For example, in my testing case the monitor and notebook has following common modes and any one of them can reproduce the blank screen using above procedure. 1024x768 800x600 640x480 Reproduce rate : 100% Reproduced on : PinTrail (PineView), HuronRiver (SandyBridge)
Finally I get workaround this issue by reverting two xorg intel driver (xf86-video-intel) commits. - Mark outputs as DPMSModeOn and restore backlight at mode set http://cgit.freedesktop.org/xorg/driver/xf86-video-intel/commit/?id=33c08882c0d551afb28baef643279901dcc65fa9 - display: outputs are enabled automatically by KMS http://cgit.freedesktop.org/xorg/driver/xf86-video-intel/commit/?id=19c48d3b3f33582baa87a9b3a9189e320e4cea45 This leads to the commit below revived. By reading the code I think it forces to set DPMS to ON after the CRTC set. This special handling for DPMS was considered redundant to recent kernels because KMS do it automatically. - Re-enable disabled outputs after rotation The server may have made a DPMS call before doing rotation, so after we do the mode set with the rotated framebuffer, we need to re-enable the corresponding output(s). Fixes bug #20573. http://cgit.freedesktop.org/xorg/driver/xf86-video-intel/commit/?id=bedc894a565ce3c7a50990e3f78953fc2432ad40 Maybe the kernel still have discrepancy in DPMS that's not addressed ..
Since this is a problem of inconsistent kernel DPMS property. Mark this as dup of bko#24982. *** This bug has been marked as a duplicate of bug 24982 ***