RE: [PATCH 2/2] net: ethernet: Add driver for Sunplus SP7021

quoted

I don't know how to implement STP in L2 switch like SP7021.

That is the nice thing about using Linux. It already knows how to implement
STP. The bridge will do it for you. You just need to add the callbacks in the
driver which are needed. Please take a look at other switchdev drivers.

quoted

If this is acceptable, I'd like to have Ethernet of SP7021 have two
operation
modes:
 - Dual NIC mode
 - Single NIC with 2-port frame-flooding hub mode

No, sorry. Do it correctly, or do not do it. Please start with a clean driver doing
Dual NIC mode. You can add L2 support later, once you have done the research
to understand switchdev, etc.

Sorry, I will go with Dual NIC mode. I'll do a whole cleanup on driver for this.
Please kindly review again.

I need time to study more about switchdev and propose a plan to high
management of company. However, Sunplus is not a networking company, 
but targets on Linux-based industrial control, autonomous mobile robot, ...

quoted

RMII pins of PHY ports of SP7021 are multiplexable. I'd like to switch
RMII pins of the second PHY for other use if single NIC mode is used.
In fact, some SP7021 boards have dual Ethernet and some have only one
Ethernet. We really need the two operation modes.

Only using a subset of ports in a switch is common. The common binding for
DSA switches is described in:

Documentation/devicetree/bindings/net/dsa/dsa.yaml and for example
Documentation/devicetree/bindings/net/dsa/hirschmann,hellcreek.yaml is a
memory mapped switch. Notice the reg numbers:

           ethernet-ports {
                #address-cells = <1>;
                #size-cells = <0>;

                port@0 {
                    reg = <0>;
                    label = "cpu";
                    ethernet = <&gmac0>;
                };

                port@2 {
                    reg = <2>;
                    label = "lan0";
                    phy-handle = <&phy1>;
                };

reg = <1> is missing in this example. Port 1 of the switch is not used. You can
do the same with a 2 port switch, when you don't want to make use of a port.
Just don't list it in DT.

Thank you for routing me to the document.
Now I know there are switch device examples in folder dsa/.
We can refer to them when we want to make a switch.

quoted

After looking up some data, I find RMC means reserved multi-cast.
RMC packets means packets with DA = 0x0180c2000000, 0x0180c2000002 ~
0x0180c200000f, except the PAUSE packet (DA = 0x0180c2000001)

Ah, good. BPDUs use 01:80:C2:00:00:00. So they will be passed when the port is
in blocking mode. PTP uses 01:80:C2:00:00:0E. So the hardware designers
appear to of designed a proper L2 switch with everything you need for a
managed switch. What is missing is software. The more i learn about this
hardware, the more i've convinced you need to write proper Linux support for
it, not your mode hacks.

    Andrew

Thanks for confirming that the L2 switch is good enough for switch device.
Actually, the IP was licensed from other company long ago. We don’t know 
all details.