This problem still exists in Ubuntu Focal Fossa (development branch) 20.04 with linux-image-5.4.0-21-generic. It also exists in linux-image-unsigned-5.6.2-050602-generic_5.6.2-050602.202004020822_amd64.deb
With linux-image-5.4.0-21-generic I didn't get any error messages after "insmod b44" in recovery mode. Also I normally booted linux-image-5.4.0-21-generic with mem=1G (limiting available memory to 1 GB) twice and also didn't get error messages after "sudo insmod b44". These symptoms are consistent with the hypothesis that swiotlb bounce buffers normally get allocated above 1 GB, causing a problem for b44 because the device can't do DMA above 1 GB and the driver can't handle this situation. That's the same problem discussed in this thread from 2011 https://groups.google.com/forum/#!topic/linux.kernel/GEx80ZCue1o
Obviously limiting memory to 1 GB has an unacceptable performance penalty, but it's nice to have at least one way to get working Ethernet.
This problem still exists in Ubuntu Focal Fossa (development branch) 20.04 with linux-image- 5.4.0-21- generic. It also exists in linux-image- unsigned- 5.6.2-050602- generic_ 5.6.2-050602. 202004020822_ amd64.deb
With linux-image- 5.4.0-21- generic I didn't get any error messages after "insmod b44" in recovery mode. Also I normally booted linux-image- 5.4.0-21- generic with mem=1G (limiting available memory to 1 GB) twice and also didn't get error messages after "sudo insmod b44". These symptoms are consistent with the hypothesis that swiotlb bounce buffers normally get allocated above 1 GB, causing a problem for b44 because the device can't do DMA above 1 GB and the driver can't handle this situation. That's the same problem discussed in this thread from 2011 https:/ /groups. google. com/forum/ #!topic/ linux.kernel/ GEx80ZCue1o
Obviously limiting memory to 1 GB has an unacceptable performance penalty, but it's nice to have at least one way to get working Ethernet.