See also these reports on the linuxppc list:

https://lore.kernel.org/linuxppc-dev/CANtoAtPcRGHafb7LddtrY5g43m82txS_mY3WO_ZtJ+pfuLvKaw@mail.gmail.com/#t
https://lore.kernel.org/linuxppc-dev/4424cb7b-2655-c6f3-ec56-fa1b4f31e21d@physik.fu-berlin.de/

Ben.

-- 
Ben Hutchings
Absolutum obsoletum. (If it works, it's out of date.) - Stafford Beer