I am also affected by this bug after upgrading to Xenial and trying to use radeon KMS. My system will only boot with `nomodeset` or `radeon.modeset=0`. Futhermore, attempting `sudo modprobe radeon modeset=1` after booting with `nomodeset` results in the same error state: screen goes blank, monitor's "No signal detected" message appears. Sometimes the machine reboots, but not always.
I have a Radeon HD5770 card. I will try to attach logs via apport -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1568211 Title: no UMS support in radeon module Status in linux package in Ubuntu: Incomplete Bug description: I upgraded overnight from Wily to Xenial. The system will not boot. Only a blank screen after grub loads the kernel. The recovery kernel loads fine and I was able to find the following messages: [drm] VGACON disable radeon kernel modesetting [drm:radeon_init [radeon]] *ERROR* no UMS support in radeon module! The recovery kernel command line had a nomodeset parameter that was not in the main kernel command line. Adding the nomodeset parameter the main kernel command line finally booted the system. It's kind of ugly but it seems to work. Note: For what it's worth I reported a similar issue against several Utopic kernels (bug #1407505). There was a back and forth with jsalisbury until a kernel finally worked. I have had no problems until today. Hope that helps. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1568211/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
