DRA821U: QSGMII_Sub

Yong,

Below is the explanation I received from the ethernet expert.

"QSGMII is a quad-port of SGMII onto a single SERDES lane. That is 4 ports of the switch can be merged onto a single lane of the SERDES.

The QSGMII port specifies which SERDES lane is used for the QSGMII module.

QSGMII_SUB is a subordinate port of a QSGMII SERDES lane. The QSGMII_SUB does not use or require a CPSW SERDES lane as it is a subordinate port to a QSGMII.

So if ports 1-8 were

1 QSGMII_SUB

2 QSGMII_SUB

3 QSGMII

4 QSGMII_SUB

5 QSGMII_SUB

6 QSGMII_SUB

7 QSGMII_SUB

8 QSGMII

The SERDES port for the CPSW port 3 would be the base lane for the first QSGMII, and ports 1, 2, and 4 are the three other subordinate ports for the first QSGMII on CPSW port 3 SERDES link.

Ports 5, 6, and 7 are the subordinate ports for the second QSGMII on CPSW port 8 SERDES. That is only CPSW port 3 and 8 will use SERDES lanes.

That is the QSGMII can be placed on any CPSW port SERDES lane, and the other ports can be put under that port.

The first 3 QSGMII_SUB ports will be placed on the first QSGMII[0], that is if CPSW ports 7 and 8 are configured for QSGMII and all the rest are for QSGMII_SUB, ports 1, 2, and 3 will be attached to CPSW port 7 QSGMII SERDES lane."

Thanks