I recently configured my new PC with Ubuntu 20.04.3 LTS. The PC has an ASUS ProArt B550-Creator motherboard with an AMD 5700G CPU. I selected this motherboard because it features 2 Thunderbolt 4 ports. The boot process takes a very long time (nearly 2 minutes!) and I noticed several error messages in the boot log that may have to do with this:
[ 21.554202] thunderbolt 0000:05:00.0: AMD-Vi: Event logged [IO_PAGE_FAULT domain=0x0008 address=0xc5c9e400 flags=0x0020]
[ 42.034409] thunderbolt 0000:05:00.0: AMD-Vi: Event logged [IO_PAGE_FAULT domain=0x0008 address=0xc5c9e500 flags=0x0020]
[ 62.514241] thunderbolt 0000:05:00.0: AMD-Vi: Event logged [IO_PAGE_FAULT domain=0x0008 address=0xc5c9e600 flags=0x0020]
[ 82.990546] thunderbolt 0000:05:00.0: failed to send driver ready to ICM
[ 82.990943] thunderbolt: probe of 0000:05:00.0 failed with error -110
To check if this is a hardware problem, I also configured this PC to boot Windows 10, but then the PC boots in just 10 seconds without any errors, so it must be a Ubuntu problem I think. Can someone advice me on tracking down this problem ?
EDIT:
Following suggestions from @galexite I disabled 'Fast Boot' and booted with iommu=soft and iommu=off. Both options resulted in the [IO_PAGE_FAULT...] lines to be replaced with [ 82.990461] thunderbolt 0000:05:00.0: failed to send driver ready to ICM [ 82.990774] thunderbolt: probe of 0000:05:00.0 failed with error -110 . (and boot time increased even more, in case of iommu=off by another 9 seconds...)