This patch derives the command descriptor fetch count from the actual
FIFO size advertised by the hardware. Fetching command descriptors
one at a time is a performance bottleneck for small blocks, especially
on hardware with multiple pipes. Even moreso if the HW has few rings.
Signed-off-by: NPascal van Leeuwen <pvanleeuwen@verimatrix.com>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>