Created attachment 190021 [details] Kernel logs from running both test at the same time and from running the second test only.. Built-in tests are enabled by the module "option radeon test=3". The integer value bits are used as flags what test to run on the module load. Running both test takes about 1-2 minutes to complete. The first one turns off the display and trashes the system in a way that the first key pressed hangs it hard - no flashing LEDs, no Magic SysRq. --- The first test moves data from system ram to video ram and back. It runs for about a minute. During that time the monitor is turning off and on again (DELLs do that if DPMS signaling is not exactly right, it's connected on DVI port). The rest of the system seems to function. Boot loading seams to finish and sometimes I can salvage complete kernel message log. Pressing CapsLock turns on its LED, but second press have no effect. Even pressing Magic SysRq first doesn't provide any control of the system. It hangs hard and only reset helps. The seconds test is about syncing between GPU rings. It seems to finish without error if run after the first one. However if I run it alone with "test=2", I get a bunch of timeouts, "GPU lockup" and other errors. When run alone the test doesn't prevent setting of working graphic mode. My videocard is Radeon HD5670 (Redwood). I have confirmation that the same happens on Tahiti chipsets. I have tried 3.17 (the oldest kernel I had) and 4.2.3 (latest release at this date), the bug is present on all of them. (Hang may differ, but this seems related on build parameters.) I've reported the bug to freedesktop bugzilla a month ago, but so far nobody have looked into it. https://bugs.freedesktop.org/show_bug.cgi?id=91961