Rcb Setup Pseudo Code; Receive Buffer Descriptors; Figure 15: Receive Producer Ring Rcb Setup - Broadcom NetXtreme/NetLink BCM5718 Series Programmer's Manual

BCM5718 Programmer's Guide

RCB Setup Pseudo Code

An example of setting up receive producer ring RCB:
Content of Pointer_to_RX_PRODUCER_RING_RCB + 0x00 = Host address of standard receive producer ring
high 32.
Content of Pointer_to_RX_PRODUCER_RING_RCB + 0x04 = Host address of standard receive producer ring
low 32.
Content of Pointer_to_RX_PRODUCER_RING_RCB + 0x0a = No flags.
Content of Pointer_to_RX_PRODUCER_RING_RCB + 0x08 = Max packet size of 1522.
Content of Pointer_to_RX_PRODUCER_RING_RCB + 0x0c = Internal Memory address for device copy of ring.
Figure 15 shows the standard ring RCB for the setup of a host-based standard producer ring.
Receive Buffer Descriptors (BDs) begin on the Receive Producer Ring. The host device driver will populate the
receive producer ring with a specified number of BDs supported by the receive producer ring (see
Size Register (offset: 0x43C)" on page
into internal memory. The Receive MTU Size register (see
page 316) specifies the largest packet accepted by the RX MAC; packets larger than the Receive MTU are
marked oversized and are discarded.
Offset
0x00
0x04
0x08
0x0c
Standard Producer Ring RCB

Receive Buffer Descriptors

The Receive Buffer Descriptor is a data structure in host memory. It is the basic element that makes up each
receive producer and receive return ring. The format of receive buffer descriptors can be seen in
page 78. A receive buffer descriptor has a 64-bit memory address and may be in any memory alignment and
may point to any byte boundary. For performance and CPU efficiency reasons, it is recommended that memory
be cache-aligned. The cache line size value is important for the controller to determine when to use the PCI
memory write and invalidate command. There are no requirements for memory alignment or cache line integrity
for the Ethernet controller.
Unlike send buffer descriptors, the receive buffer descriptors cannot be chained to support multiple fragments.
Broadcom
®
January 29, 2016 • 5718-PG108-R
316). When a packet is received, the RX MAC moves the packet data

Figure 15: Receive Producer Ring RCB Setup

31 16 15
Host Ring Address
Max_Len Flags
NIC Ring Address
"Receive MTU Size Register (offset: 0x43C)" on
511
0 512
BD 1
BD 2
BD 3
Standard Producer Ring
Receive Producer Ring
"Receive MTU
Std Ring
Table 11 on
Page 91