Ring Control Blocks; Send Rings; Table 10: Ring Control Block Format; Table 11: Flag Fields For A Ring - Broadcom BCM5722 Programmer's Manual

Programmer's Guide
10/15/07
R C B
ING ONTROL LOCKS
Each ring (send or receive) has a Ring Control Block (RCB) associated with it. Each RCB has the format shown in
Offset (bytes) 31
0x00
0x04
0x08
0x0c
The fields are defined as follows:
• The Host Ring Address field contains the 64-bit host address of the first element in the ring. Basically, this field tells the
controller precisely where in host memory the ring is located. This field only applies to rings that are located in host
memory. The Host_Ring_Address field contains the 64-bit address, in big-endian ordering, of the first Send BD in host
memory.
• The Flags field contains bits flags that contain control information about a given ring. The following table shows the two
flags that are defined.
Bits Name
0 RCB_FLAG_USE_EXT_RECV_BD
1 RCB_FLAG_RING_DISABLED
15:2 Reserved
• The Max_len field has a different meaning for different types of rings.
- This field indicates the number elements in the ring.
- The valid values for this field are 32, 64, 128, 256, and 512.
• The NIC Ring Address field contains the address where the BD cache is located in the internal NIC address space. This
address is only valid for Receive Producer Rings. The Send Rings and Receive Return Rings do not require this field to
be populated. The location within the NIC address map for Receive Producer Ring is provided in
Pool Configuration" on page
S R
END INGS
The BCM5755, BCM5755M, BCM5787, BCM5787M, BCM5906, BCM5906M, BCM5754, and BCM5754M devices support
only one host based Send Ring.
The Send Ring Producer Index is incremented by host software to add descriptors to the Send Ring (see
on page 45). By adding descriptors to the ring, the device is instructed to transmit packets that are composed of the buffers
pointed to by the descriptors. A single transmit packet may be composed of multiple buffers that are pointed to by multiple
send descriptors. The maximum number of send descriptors for a single packet is (0.75)*(ring size).
Document 5722-PG101-R

Table 10: Ring Control Block Format

Max_len

Table 11: Flag Fields for a Ring

Description
This bit should be used only for Receive Jumbo Rings. This bit indicates
that the ring will use extended receive buffer descriptors (see
Descriptors" on page
Note: Jumbo frames are not supported by BCM5755, BCM5755M,
BCM5787, BCM5787M, BCM5906, BCM5906M, BCM5754, or
BCM5754M.
Indicates that the ring is not in use.
Should be set to 0.
101.
Bro adco m Co rp or atio n
16 15
Host Ring Address
Reserved
46).
BCM5722
Table
Flags
"Send Buffer
"Memory Maps and
Figure 22
Descriptor Rings Page 44
10.
0