Hi All, There are several bug reports (arch and Fedora) about USB problems starting with kernel 5.14.14 (5.14.13 is ok): https://bugzilla.redhat.com/show_bug.cgi?id=2019788 https://bbs.archlinux.org/viewtopic.php?pid=2006862 And 5.16.6, which has the hub address0_mutex fixes does not fix these problems for some users. Looking at the history between those 2 commit ff0e50d3564f ("xhci: Fix command ring pointer corruption while aborting a command"): https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ff0e50d3564f stood out to me as a possible cause of this. So I've build a test 5.15.6 kernel for Fedora users with that commit reverted and 2 users have now reported that this fixes things for them (see https://bugzilla.redhat.com/show_bug.cgi?id=2019788). The reason why this stood out to me is because doing a 32 bit write over a possibly 64 bit databus to the xHCI controller may result in the hw doing a 64 bit read + modify 32 bit + 64 bit write, so I think that the following is happening after the commit: sw: read 32 bit hw: read 64 bit, return 32 bit sw: modify it sw: write 32 bit hw: read 64 bit hw: modify 32 bit of 64 bit wor5d hw: write 64 bit Which actually makes the chances of hitting the problem the commit tries to fix larger on controllers using a 64 bit data bus. Note this is just a theory, but it seems plausible to me. All problem reports are people using integrated Intel xHCI controllers which I believe are likely to use a 64 bit data-bus. Regards, Hans
