In our idle loop, use an or instruction to set PRELOADEN rather
than rewriting the contents of DMAPARAMS to DFCNTRL. The later
may re-enable the DMA engine if the idle loop is called to complete
the preload of at least one segment when a target disconnects on
an S/G segment boundary but before we have completed fetching the
next segment. This correts a hang, usually in message out phase,
when this situation occurs. This bug has been here for a long
time, so the situation is rare, but not impossible to reproduce.
It only affected Ultra2/U160 controllers.
Correct a few comments.
Extra Sanity. Make sure that SCSIEN is also turned off, along with
HDMAEN, at the end of the data phase.
27bbd0d3ef