> I added this to my tree (with my atabus changes), just after the return from
> __wdcprobe() (in the current tree, this would be in wdcattach()),
> which helps a lot. As with atabus kernel thread we do this in parallel for
> all busses, we're down to 3s to detect the ghosts, independant from the
> number of busses.

But you can't do that.  You're assuming DRDY will be asserted within
3s of BSY being deasserted, but that is NOT what the spec says.