Hi again :) My brother pointer me to an old thread from year 2010 on bugzilla.kernel.org that discusses a problem that has exactly the same symptoms as mine (https://bugzilla.kernel.org/show_bug.cgi?id=16265).
And this seems to have shed some light on this problem, it might have to do with the driver polling the video interfaces to see if new displays have been attached and the polling locks display updates for a while. Workaround 1 -------------------- If I do: echo 0 > /sys/module/drm_kms_helper/parameters/poll after booting, then the problem goes away. Strangely if I now re-enable polling with: echo 1 > /sys/module/drm_kms_helper/parameters/poll the problem does NOT come back, it stays away until next boot. Maybe this resolves some kind of "knot" the kernel + video driver have tied themselves into. Workaround 2 -------------------- Booting the machine with kernel option: drm_kms_helper.poll=0 makes the problem go away. As far as I understand these are not a real solutions, since now the machine is unable to discover new displays attached to it. This also does not explain why the problem does not exist in the intel driver package originally shipped with Ubuntu 12.04 and why it appeared in the first update. ** Bug watch added: Linux Kernel Bug Tracker #16265 http://bugzilla.kernel.org/show_bug.cgi?id=16265 -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1077512 Title: xserver-xorg-video-intel regression, video playback not smooth on external display after video driver update To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/xserver-xorg-video-intel/+bug/1077512/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
