Hello, my system is a ThinkPad T540p attached to an Ultra Dock with Debian Jessie 64bit installed. On the dock's DP an external Eizo LCD is connected and the lid of the ThinkPad is normally closed. After a resume from Suspend-to-RAM, the LCD of the ThinkPad awakes but the external LCD stays turned-off. It is possible to reactivate the external LCD manually with KDE's krandrtray. I observed this behavior with kernels 3.18.3 and newer. With kernel version 3.18.2 and older, both LCDs are reactivated after a resume automatically. Some info about the system: /proc/cpuinfo processor : 0 vendor_id : GenuineIntel cpu family : 6 model : 60 model name : Intel(R) Core(TM) i7-4700MQ CPU @ 2.40GHz lspci -k | grep -A2 VGA 00:02.0 VGA compatible controller: Intel Corporation 4th Gen Core Processor Integrated Graphics Controller (rev 06) Subsystem: Lenovo Device 221e Kernel driver in use: i915 -- 01:00.0 VGA compatible controller: NVIDIA Corporation GK208M [GeForce GT 730M] (rev a1) (-> disabled, not configured for X11!) /var/log/Xorg.0.log (II) Loading /usr/lib/xorg/modules/drivers/intel_drv.so (II) Module intel: vendor="X.Org Foundation" compiled for 1.15.99.904, module version = 2.21.15 Module class: X.Org Video Driver ABI class: X.Org Video Driver, version 18.0 (II) LoadModule: "modesetting" (II) Loading /usr/lib/xorg/modules/drivers/modesetting_drv.so (II) Module modesetting: vendor="X.Org Foundation" compiled for 1.15.99.904, module version = 0.9.0 Module class: X.Org Video Driver ABI class: X.Org Video Driver, version 18.0 ... (II) intel(0): Output eDP1 using monitor section eDP1 -> internal LCD (**) intel(0): Option "PreferredMode" "1920x1080" (--) intel(0): found backlight control interface /sys/class/backlight/intel_backlight (II) intel(0): Output VGA1 has no monitor section (II) intel(0): Output DP1 has no monitor section (II) intel(0): Output HDMI1 has no monitor section (II) intel(0): Output DP2 using monitor section DP2 -> external LCD (**) intel(0): Option "PreferredMode" "1920x1200" (II) intel(0): Output HDMI2 has no monitor section (II) intel(0): Output DP3 has no monitor section (II) intel(0): Output DP4 has no monitor section (II) intel(0): Output DP5 has no monitor section Please, let me know if you need additional debugging output. Best regards, Chris
A bisect between 3.18.2 and 3.18.3 would be really useful. Also, add drm.debug=0xe to your kernel command line and then attach the full dmesg from boot to the occurrence of the problem.
Created attachment 177791 [details] dmesg output for various test runs
Explanation of the different files in the attachment: *-01-boot: dmesg dump directly after boot and login into KDE and prior suspend to ram *-02-resume: dmesg dump directly after resume *-03-resume-extLCDreenabled: dmesg dump after manual re-activation of external LCD Note: the wrong behavior occurs for kernel 3.18.4 or newer! Up to version 3.18.3 it works fine. Sorry for the mix-up of the versions. Regards, Chris
Any news on this issue? Problem still exists with kernel 4.1. Regards, Chris
DP MST has seen lots of updates in newer kernels. Please try them. If the problem persists with latest kernels, please file a bug at the freedesktop.org bugzilla [1], referencing this bug. Thank you. [1] https://bugs.freedesktop.org/enter_bug.cgi?product=DRI&component=DRM/Intel