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Date:   Mon, 8 Nov 2021 15:52:35 +0100
From:   Andrew Lunn <andrew@lunn.ch>
To:     Wells Lu =?utf-8?B?5ZGC6Iqz6aiw?= <wells.lu@sunplus.com>
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Subject: Re: [PATCH 2/2] net: ethernet: Add driver for Sunplus SP7021
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> The switch will not recognize type of packets, regardless BPDU, PTP or any other
> packets. If turning off source-address learning function, it works like an Ethernet
> plus a 2-port hub.

So without STP, there is no way to stop an loop, and a broadcast storm
taking down your network?

Looking at the TX descriptor, there are two bits:

          [18]: force forward to port 0
          [19]: force forward to port 1

When the switch is enabled, can these two bits be used?

In the RX descriptor there is:

pkt_sp:
          000: from port0
          001: from port1
          110: soc0 loopback
          101: soc1 loopback

Are these bits used when the switch is enabled?

0.31 port control 1 (port cntl1) blocking state seems to have what you
need for STP.

    Andrew