netdev - Re: DSA: external phy address and port number of switch conflicts

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Message-ID: <c84c7215-2315-2602-2ab6-d809c918d146@gmail.com>
Date:   Thu, 13 Dec 2018 21:08:54 -0800
From:   Florian Fainelli <f.fainelli@...il.com>
To:     John Rama <john.rama01@...il.com>, netdev@...r.kernel.org,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>
Subject: Re: DSA: external phy address and port number of switch conflicts

Hello,

Le 12/13/18 à 4:12 PM, John Rama a écrit :
> Dear DSA experts
> 
> My name is John.
> 
> I'm working for our custom board which has the Marvel 88e5050 ethernet switch
> as shown below, and trying to make the system works using DSA subsystem.
> 
> I found one problem and have a question.
> 
> - System
>     - i.MX6 and Marvel 88e5050 Switch(PHY addr is 0x10)
>     - port1-5 has integrated PHY
>      - port7 is connected to Marvel 88e1510 PHY(PHY addr is 0x1)
> 
>                            0x10
>     +------------+         +-----------------+
>     |            |         | Marvel 88e5050  |
>     |            | RGMII   |           port1 |
>     |   IMX6     +---------+ port6           |
>     |            |         |           port2 |
>     |            | MDIO    |                 |
>     |            +-+-------+           port3 |
>     |            | |       |                 |
>     +------------+ |       |           port4 |
>                    |       |                 |
>                  +-+-+     |           port5 |
>                  |   |SGMII|                 |
>                  |PHY|-----| port7           |
>                  |   |     |                 |
>                  +---+     +-----------------+
>               Marvel 88e1510
>                    0x1                        
> 
> - Device Tree setting
>     In this configuration, our dts is as followings.
> 
>     dsa@0 {
>       compatible = "marvell,dsa";
>         #address-cells = <2>;
>         #size-cells = <0>;
> 
>         dsa,ethernet = <&fec>;
>         dsa,mii-bus = <&mdio>;

You are using the old binding here, you might want to switch to the new
DSA binding which would be nearly identical, except that it would be
placing the switch Device Tree node as a child node of the MDIO bus it
is connected to.

> 
>         switch@0 {
>             #address-cells = <1>;
>             #size-cells = <0>;
>             reg = <0x10 0>;    /* MDIO address 16, switch 0 in tree */
> 
>             port@1 {
>                 reg = <1>;
>                 label = "port1";
>             };
> 
>             port@2 {
>                 reg = <2>;
>                 label = "port2";
>             };
> 
>             port@3 {
>                 reg = <3>;
>                 label = "port3";
>             };
> 
>             port@4 {
>                 reg = <4>;
>                 label = "port4";
>             };
> 
>             port@5 {
>                 reg = <5>;
>                 label = "port5";
>             };
> 
>             port@6 {
>                 reg = <6>;
>                 label = "cpu";
>             };
> 
>             port@7 {
>                 reg = <7>;
>                 label = "port7";
>                 phy-handle = <&ethphy1>;
>                 phy-mode = "sgmii";
>             };                                       
>         };
>      };
> 
>     mdio: mdio {
>         #address-cells = <1>;
>         #size-cells = <0>;
> 
>         ethphy1: 88e1510{
>             reg = <1>;
>             phy-mode = "sgmii";
>         };
> 
>     };
>                                 
> - Problem
>     dsa_slave_phy_connect() for port 7 results in attaching Generic PHY,
>     as shown in the following log, which is unexpected result.
>     dsa dsa@0 port7 (uninitialized): attached PHY at address 1 [Generic PHY]
> 
>     This is because port7 PHY addr (reg=<1>) and the port1 port number (reg=<1)> is conflicting.
>     If I comment out the port1 setting from DTS, I can get following log,
>     everything working fine and
> 
>     dsa dsa@0 port7 (uninitialized): attached PHY at address 1 [Marvel 88E1510]
> 
>     I'm using a little bit old kernel,4.1.15.
>     So I checked the latest code of linux-next, but it seems there is similar problem.

I would recommend checking a newer kernel anyway which would have
support for the mv88e6xxx internal MDIO bus as it might allow you to
solve that specific problem. A kernel that contains
a3c53be55c955b7150cda17874c3fcb4eeb97a89 ("net: dsa: mv88e6xxx: Support
multiple MDIO busses") might work better and actually help here, though
I don't know enough about that specific switch model, Andrew or Vivien
would.

> 
> - Question
>     Is this system configuration is not supported by DSA ?

This does not appear to be a DSA specific problem, this is more about
possible MDIO bus address conflicts. I am not sure how well this is
going to work; but it might be possible to create a virtual mdio-mux
driver which is pinmuxing the MDIO pins on the imx6 chip when there is a
possible MDIO bus address conflict, such that you can access each
address without conflicts. This may not be working given that the switch
driver might be doing concurrent accesses to the bus while the external
PHY is being polled...

>     Or am I misunderstand something ?
>     Any insights are really appreciated.
> 
> John
> 


-- 
Florian