The pp_fifo decides whether top = bottom means empty or full based
on whether the previous operation was a push or a pop.
If the fifo performs both in one cycle, it sets the previous op to
pop. That means that a full fifo being added a character and removed
one at the same time becomes empty.
Instead, just leave the previous op alone. If the fifo was empty, it
remains so, if it was full ditto.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
The shared variable used for FIFO memory is not VHDL 2008 compliant.
I can't see why it needs to be a shared variable since reads and writes
update top and bottom synchronously, meaning they don't need same cycle
access to the FIFO memory.
Signed-off-by: Anton Blanchard <anton@linux.ibm.com>
Benjamin Herrenschmidt