kworker/u4:1+tau stuck on G4 Sawtooth

Good Morning!

I recently acquired a pair of G4 Sawtooth towers that are basically 
identical except for CPU and RAM - one is 450Mhz/384M and the other is 
500Mhz/1G. When I initially setup the pair they were running the 
6.12.6-1 kernel from the previous NETINST iso and everything ran fine 
but I noticed that the CPU load reported under top, etc. remained at 
1.00 across the board after the systems settled down from the initial 
boot. I ran into the same problem with my initial installs of Sid on 
Sparc64 last year and the problem persisted until the kernel was 
upgraded to 6.7.7-1, so I thought maybe I just needed to wait for a 
kernel update or two on powerpc for the issue, whatever it was, to get 
flushed out. Well, I've been updating both machines frequently and they 
are both now running 6.12.21-1 and the quirk is still there so I decided 
to do a little looking. If you do a quick ps aux on the systems they 
both show kworker/u4:1+tau in state D, so I did a quick iostat -p on 
both systems which show that on the system disk there are ~1.73tps and 
~33kB/s read and 4.6kB/s written with nothing running on the system 
other than my login. In /proc the status for that PID shows:

Name:   kworker/u4:1+tau
Umask:  0000
State:  D (disk sleep)
Tgid:   19
Ngid:   0
Pid:    19
PPid:   2

...

and iotop shows virtually nothing hitting the disk, not even the swapfile.

Now, it has been more than a hot minute since I did anything with the 
kernel other than do a recompile here and there, so I may be way off 
target here. I am just trying to figure out why the load sticks at 1.00 
and this kworker seems to hang on these 2 G4s but I am seeing nothing 
similar on ARM, x86, x86_64 or Sparc64 with similar kernel releases.

Cheers,
Bill