Did this issue start happening after an update/upgrade? Was there a prior kernel version where you were not having this particular problem?
Would it be possible for you to test the latest upstream kernel? Refer to https://wiki.ubuntu.com/KernelMainlineBuilds . Please test the latest v4.11 kernel[0]. If this bug is fixed in the mainline kernel, please add the following tag 'kernel-fixed-upstream'. If the mainline kernel does not fix this bug, please add the tag: 'kernel-bug-exists-upstream'. Once testing of the upstream kernel is complete, please mark this bug as "Confirmed". Thanks in advance. [0] http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.11-rc4 -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux-lts-trusty in Ubuntu. https://bugs.launchpad.net/bugs/1675996 Title: Default nouveau video driver creates garbled display (White 24" iMac w/ NVIDIA GeForce 7600 GT) Status in linux-lts-trusty package in Ubuntu: New Bug description: My White iMac 24" is unable to start an X-Windows session with the Ubuntu Install DVD. I am running Ubuntu 14.04.5 LTS (Trusty Tahir) It looks like the kernel/initrd is loading the nouveau_304 driver, but this results in a garbled screen (see attachment). For even more information, please see: http://mymanthemaker.blogspot.hk/2017/03/getting-white-24-core-2-duo-imac-to.html http://mymanthemaker.blogspot.hk/2017/03/imac-ubuntu-install-gone-wrong-install.html For exhaustive detail and many screen shots. The error messages I see in dmesg (thousands of them) are: nouveau 0000:01:00.0: fifo: DMA_PUSHER - ch 1 [Xorg[2121]] get 00018000 put 000180a0 state 80000000 (err: INVALID_CMD) push 00000000 and nouveau 0000:01:00.0: Xorg[2121]: failed to idle channel 1 [Xorg[2121]] and EQ overflowing. Additional events will be discarded until existing events are processed. ProblemType: Bug DistroRelease: Ubuntu 14.04 Package: linux-image-4.4.0-31-generic 4.4.0-31.50~14.04.1 ProcVersionSignature: Ubuntu 4.4.0-31.50~14.04.1-generic 4.4.13 Uname: Linux 4.4.0-31-generic x86_64 ApportVersion: 2.14.1-0ubuntu3.21 Architecture: amd64 Date: Sat Mar 25 06:39:17 2017 ProcEnviron: TERM=xterm PATH=(custom, no user) XDG_RUNTIME_DIR=<set> LANG=en_US.UTF-8 SHELL=/bin/bash SourcePackage: linux-lts-xenial UpgradeStatus: No upgrade log present (probably fresh install) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux-lts-trusty/+bug/1675996/+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
