Created attachment 288979 [details] dmesg from 5.7.0.994 boot attempt Applies to a 2015 5k iMac 27" with AMD r9390x video card. I was asked to file this as I have been testing 5.3, 5.4, 5.6 and 5.7 kernel, all of which boot very slowly (> 3 minutes to working desktop), and also have delayed wakeup from display sleep (~2 minutes) and delayed shutdown (~ 2 minutes). dmesg and systemd analysis for these boots have been posted in bugs.launchpad.net/bugs/1875211. I have been asked to test several of the 5.7 rc kernels and the latest version (5.7.0.994). Only one of these versions would boot at all (rc3); the other rc kernels would only get as far as the login screen, and 5.7.0.994 wouldn't get even that far. Attached is the dmesg to the 5.7.0.994 boot attempt.
Did this system ever work? If so when and can you bisect?
(In reply to Alex Deucher from comment #1) > Did this system ever work? If so when and can you bisect? Yes, it works well with the 4.15 kernel. And I did bisect to the extent of finding out the point at which the slow boot occurred. You can follow it here: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1874104 In a nutshell, kernels 5.0, 5.1 and 5.2 are fine. The last good (i.e. normal booting) kernel was 5.2.21. Kernel 5.3.rc1 was the first slow booting version. Kernels I tried that are slow booting are 5.3.0, 5.3.1, 5.6, and the 5.6 rc's leading up to 5.7.0.994. I don't think I am technically competent enough to dissect within a kernel.