Date:   Wed, 16 Feb 2022 08:55:17 +0000
From:   "Moltmann, Tobias" <Tobias.Moltmann@...mens.com>
To:     Andrew Lunn <andrew@...n.ch>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: DSA and Marvell Switch Drivers

Hello,

I would first rewrite my questions and provide some information's and add some of Andrews answer to it as well.
As I learned it would be helpful to address the "netdev list" to get (hopefully) even more help. 
So please feel free to provide some feedback, thank you!

The issue we face comes along with an Kernel upgrade from 4.4.xxx to now 5.10.xx. It is all industrial-based hardware, so 
no classical PC or something. On the hardware we have an x86 CPU, an IGB -> Marvell Switch (Marvell 88E6176) ->
and two PHY's connected there.

Very roughly the way it worked/run with the 4.4 Kernel:

- mv88e6xxx_init() called - registered the driver
- IGB driver loaded, started probing
- within the probing we set up an MDIO bus (name: igb MDIO, id: 0000:01:00.0_mii)
- the libphy does a first scan with no result due to some other missing stuff - at this point it is ok
- also within the igb probing we set up an dsa_platform_data struct and run a platform_device_register()
- this triggers the DSA driver
- mv88e6352_probe() is called our Marvell switch is detected
- a new DSA slave MDIO bus is been brought up automatically
- mdiobus_scan() there register our two PHY devices 
- everything is working :)


Now in the 5.10 Kernel, as there are the rewritten DSA/Marvell drivers included, the upper "stuff" is not working anymore.
So far so good... Due to the fact, that the DSA/Marvell drivers aren't platform driver anymore the trigger with the platform_device_register()
has no effect any more. I suggest we need to end up in the new mv88e6xxx_probe() function in drivers/net/dsa/mv88e6xxx/chip.c.
As there is all the probing, register of DSA stuff included. 
I added some "printf" in the module init parts in the chip.c file as well as in the /net/dsa/dsa.c - and I do see them in the
Kernel logfile after startup. Everything else I added as output, does not show up.

Andrew already pointed out, that you now have to set up (as example) the following:

static struct dsa_mv88e6xxx_pdata dsa_mv88e6xxx_pdata = {
        .cd = {
                .port_names[0] = NULL,
                .port_names[1] = "cpu",
                .port_names[2] = "red",
                .port_names[3] = "blue",
                .port_names[4] = "green",
                .port_names[5] = NULL,
                .port_names[6] = NULL,
                .port_names[7] = NULL,
                .port_names[8] = "waic0",
        },
        .compatible = "marvell,mv88e6190",
        .enabled_ports = BIT(1) | BIT(2) | BIT(3) | BIT(4) | BIT(8),
        .eeprom_len = 65536,
};

static const struct mdio_board_info bdinfo = {
        .bus_id = "gpio-0",
        .modalias = "mv88e6085",
        .mdio_addr = 0,
        .platform_data = &dsa_mv88e6xxx_pdata, };

        dsa_mv88e6xxx_pdata.netdev = dev_get_by_name(&init_net, "eth0");
        if (!dsa_mv88e6xxx_pdata.netdev) {
                dev_err(dev, "Error finding Ethernet device\n");
                return -ENODEV;
        }

        err = mdiobus_register_board_info(&bdinfo, 1);
        if (err) {
                dev_err(dev, "Error setting up MDIO board info\n");
                goto out;
        }

I did a bunch of tries with this information's, put in our .bus_id, changed the port_names accordingly, switched the board register up and down etc. 
but it still does not succeed ☹ 
As Andrew also mentioned there is no mainline example and I'm also a bit confused that I haven't found (might be limitated to my person)
any example somewhere out there which will put some light in our darkness...

So I would appreciate any help from you guys.
You can also contact me directly - feel free if you think it a more optimized way. 
I'll share my solution/information's if it works someday ...

Kind regards,
Tobias

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