Am 2021-06-01 11:59, schrieb Linus Walleij:

Just regarding all registers/memory cells in a register page
as default volatile (which is what we do a lot of the time)
has its upsides: bugs like this doesn't happen.

I don't think this is the bug here. If it is really a write-only 
register
the problem is the read in RMW. Because reading the register will return
the input value instead of the (previously written) output value.

-michael