The solution to my problem was given to me in #ubuntu on Freenode. Kernel parameter radeon.dpm=0. That's dynamic power management. I think the clue was that everything works fine when the laptop is not plugged in, so the fine young man probably thought there was a bug in dynamic power management. Disabling it allows my laptop to be used now (first time in 6 or so months!). Thank you for your time and energy.
This can be closed. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1855024 Title: Computer Stops Responding Shortly After Logging In To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1855024/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
