Hello everyone.
After seeing that the 5.11 kernel was no longer experimental, I decided to download it and give it a try. Unfortunately, if I pick it in GRUB, my computer freezes on a black screen and just won’t boot. It becomes completely unresponsive, and neither the TTY shortcuts, nor REISUB work, and I have to hard shutdown out of it.
I asked on Reddit and someone suggested that it was because I downloaded the kernel via the GUI and some components may not have been installed. Deleting it and reinstalling it with mhwd-kernel results in the same freeze on a black screen.
I have no idea what the problem is, upgrading to 5.10 from 5.9 was as simple as clicking on “download” and rebooting.
In case that might help, I’m using the Plasma desktop, and both my CPU and GPU are AMD (A6, and Radeon R4, respectively), so no Nvidia shenanigans. I don’t think it is related to the recent update either, because the other kernels work fine.
I still have 5.9 and 5.10 installed so it isn’t that big a deal for the time being, but I would like to get 5.11 working eventually. Thanks in advance 
This can be a lot of things - mostly of which I know nothing - simply because I am not using AMD.
But it strikes me as odd if your system works with 5.10 and not 5.11 as this indicates a problem with a 5.11 kernel module and despite my lack of knowledge on the AMD front such issues often fall into the display driver category - maybe the mhwd default settings needs tweaking for 5.11 - I really don’t know.
But one thing - a thing I immediately would test - is to boot the system on an ISO with 5.11 and check if the issue persist.
add version 54 ( LTS ) and reboot
press Esc to see Grub go in Details > select & check
Thanks for the reply.
I was also thinking it could be graphics-related, but it strikes me as odd that the other kernels work out of the box, no fuss and no tweaking required. Maybe 5.11 is still not quite ready for prime time, and at this point I think I’ll just wait a wee while for the issue to be fixed.
I would try booting an ISO as you suggested, but the ones up for download on the website are still on 5.9. As I said, 5.10 works and there are still the LTS kernels should I need to switch, so there is no real urgency.
Try adding the kernel option iommu=soft in the kernel boot line in GRUB and boot it (using ctrl+x or f10). It’s probably the kernel bug 212133. I published it in the bugzilla of the Linux kernel after publishing it here weeks ago. It’s a kernel bug on AMD hardware. The kernel staff is correcting the kernels.