Jumbo frame support for BGE_ASICREV_BCM5714

[Vijay Singh]

> As you know, BCM5714, BCM5715 and BCM5780 use unique jumbo frame
> scheme that is not compatible with other controllers. All other
> Broadcom controllers have better jumbo frame scheme. These
> controllers have one send ring, one standard receive producer ring
> and one receive return ring. In order to receive jumbo frames on
> these controllers you have to increase Rx buffer size to hold 9k
> sized jumbo frame. Two Rx modes(standard Rx BDs and extended Rx
> BDs) are supported for these controllers. Using extended Rx BDs on
> BCM5714/BCM5715/BCM5780 reduces the number of Rx BDs to 256 entries
> which shall reduce the performance. I would use standard Rx BDs to
> hold 512 entries for RX buffers.
>
> I think I received jumbo frame support request for these
> controllers in past. At that time I had no interests on
> implementing it due to severe implementation differences. What is
> your main reason to use jumbo frame on this controller? What is
> your expectation on performance numbers? I guess no other OSes
> support jumbo frame on this controller.

Hi Pyun, I am stuck with this NIC due to it being the one present in
the HW platform that I have to support. The performance is expectation
is mainly for apps that use large payloads (where something TSO would
have helped).

-vijay