AM3357: Dual MACs configured for a HUB rather than a SWITCH

Tool/software:

Question setting up the ALE table and configuration of the Ethernet Subsystem of the AM335x Sitara Processor

This is a section from the data sheet describing how to set up dual mac mode with seperation (at the switch) between the host/port1, host/port2 networks. This works.

14.3.2.10.2 Dual Mac Mode

When operating in dual mac mode the intention is to transfer packets between ports 0 and 1 and ports 0

and 2, but not between ports 1 and 2. Each CPGMAC_SL appears as a single MAC with no bridging

between MAC’s. Each CPGMAC_SL has at least one unique (not the same) mac address.

Dual mac mode is configured as described below:

• Set the ale_vlan_aware bit in the ALE_Control register. This bit configures the ALE to process in vlan

aware mode.The CPSW_3G vlan aware bit (vlan_aware in CPSW_Control) determines how packets

VLAN’s are processed on CPGMAC_SL egress and does not affect how the ALE processes packets or

the packet destination. The CPSW_3G vlan aware bit may be set or not as required (must be set if

VLAN’s are to exit the switch).

• Configure the Port 1 to Port 0 VLAN

Add a VLAN Table Entry with ports 0 and 1 as members (clear the flood masks).

Add a VLAN/Unicast Address Table Entry with the Port1/0 VLAN and a port number of 0. Packets

received on port 1 with this unicast address will be sent only to port 0 (egress). If multiple mac addresses

are desired for this port then multiple entries of this type may be configured.

• Configure the Port 2 to Port 0 VLAN

Add a VLAN Table Entry with ports 0 and 2 as members (clear the flood masks).

Add a VLAN/Unicast Address Table Entry with the Port2/0 VLAN and a port number of 0. Packets

received on port 2 with this unicast address will be sent only to port 0 (egress). If multiple mac addresses

are desired for this port then multiple entries of this type may be configured.

• Packets from the host (port 0) to ports 1 and 2 should be directed. If directed packets are not desired

then VLAN with addresses can be added for both destination ports.

• Select the dual mac mode on the port 0 FIFO by setting tx_in_sel[1:0] = 01 in P0_Tx_In_Ctl. The

intention of this mode is to allow packets from both ethernet ports to be written into the FIFO without

one port starving the other port.

• The priority levels may be configured such that packets received on port 1 egress on one CPDMA RX

channel while packets received on port 2 egress on a different CPDMA RX channel.

We are  looking for a similar description for a dual mac setup where both ports are on the same subnet and all ports see all traffic. We need this because we’d like to use a hub function rather than a switch function allowing all packets to be presented to the HOST, MAC1 and MAC2. The design daisy chains multiple AM335X processors together with other boards.