Created attachment 212441 [details] Default dmesg Hi all, I tried to connect an external display to a Lenovo X260. It doen't matter if it is connected via HDMI or m-DP. Every time I activate the connected display (e.g. Xubuntu - Settings->Display->Select External Display->Use this output) the system will freeze completely. A reboot is possible by holding the power button for 4 seconds only. It is not possible to get a dmesg output which shows a kernel oops / panic because the cpu seems to stop working completely. I will attach a default dmesg output and a dmesg output with drm.debug. Even trying to create a crash dump via pstore efi backend creates no crash dumps. To make sure that this issue is not associated with https://bugzilla.kernel.org/show_bug.cgi?id=110941 I added intel_pstate=no_hwp to kernel command line. Best regards, Dennis
Created attachment 212451 [details] drm.debug dmesg
Some additional information: This freeze will not occur with Ubuntu wily kernel <= 4.4.6. It starts freezing with Ubuntu wily kernel >= 4.5. So maybe it looks like a regression? Using Ubuntu xenial it freezes not dependent on the kernel version. I checked it with default kernel of beta2 (Ubuntu-4.4.0-15) and the latest kernel Ubuntu-4.4.0-18.34.
I can not reproduce this crash at drm-intel-nightly since 25th April. So it seems to be fixed now.