Re: [PATCH net-next v9] net: mdio: Add RTL9300 MDIO driver

[Andrew Lunn <andrew@lunn.ch>]

> Ah I get it. It's about tracking the current page for a particular 
> device address and using that instead of 0xfff in 
> FIELD_PREP(PHY_CTRL_MAIN_PAGE, 0xfff). I'm not sure it's going to work 
> generically. Realtek switches know about Realtek PHYs but I've seen 
> plenty of other PHYs that do paging via addresses other than 0x1f 
> (Marvell 88E1111 for example uses 0x1d for its extaddr, some Broadcom 
> PHYs seem to use 0x1c). I'm not sure how many systems are mixing vendors 
> for C22 PHYs (the Zyxel boards seem to have Marvell AQR 10G PHYs but 
> that's C45).

It is worse than that. The switch needs to change the page itself:

static int rtlgen_read_status(struct phy_device *phydev)
{
        int ret, val;

        ret = genphy_read_status(phydev);
        if (ret < 0)
                return ret;

        if (!phydev->link)
                return 0;

        val = phy_read_paged(phydev, 0xa43, 0x12);
        if (val < 0)
                return val;

        rtlgen_decode_physr(phydev, val);

It needs to read register 0x12 from page 0xa43.

I do agree this cannot work in the general case. Which is why i asked
about what the limitations are for configuring the MAC in software.

	Andrew