Re: [PATCH net-next v6 3/3] net: ethernet: ti: am65-cpsw: Add support for SERDES configuration

[Geert Uytterhoeven <geert@linux-m68k.org>]

Hi Siddharth,

On Wed, Jan 4, 2023 at 11:37 AM Siddharth Vadapalli <s-vadapalli@ti.com> wrote:
> Use PHY framework APIs to initialize the SERDES PHY connected to CPSW MAC.
>
> Define the functions am65_cpsw_disable_phy(), am65_cpsw_enable_phy(),
> am65_cpsw_disable_serdes_phy() and am65_cpsw_enable_serdes_phy().
>
> Add new member "serdes_phy" to struct "am65_cpsw_slave_data" to store the
> SERDES PHY for each port, if it exists. Use it later while disabling the
> SERDES PHY for each port.
>
> Power on and initialize the SerDes PHY in am65_cpsw_nuss_init_slave_ports()
> by invoking am65_cpsw_enable_serdes_phy().
>
> Power off the SerDes PHY in am65_cpsw_nuss_remove() by invoking
> am65_cpsw_disable_serdes_phy().
>
> Signed-off-by: Siddharth Vadapalli <s-vadapalli@ti.com>

Thanks for your patch, which is now commit dab2b265dd23ef8f ("net:
ethernet: ti: am65-cpsw: Add support for SERDES configuration")
in net-next.

> --- a/drivers/net/ethernet/ti/am65-cpsw-nuss.c
> +++ b/drivers/net/ethernet/ti/am65-cpsw-nuss.c
> @@ -1416,6 +1416,68 @@ static const struct net_device_ops am65_cpsw_nuss_netdev_ops = {
>         .ndo_setup_tc           = am65_cpsw_qos_ndo_setup_tc,
>  };
>
> +static void am65_cpsw_disable_phy(struct phy *phy)
> +{
> +       phy_power_off(phy);
> +       phy_exit(phy);
> +}
> +
> +static int am65_cpsw_enable_phy(struct phy *phy)
> +{
> +       int ret;
> +
> +       ret = phy_init(phy);
> +       if (ret < 0)
> +               return ret;
> +
> +       ret = phy_power_on(phy);
> +       if (ret < 0) {
> +               phy_exit(phy);
> +               return ret;
> +       }
> +
> +       return 0;
> +}
> +
> +static void am65_cpsw_disable_serdes_phy(struct am65_cpsw_common *common)
> +{
> +       struct am65_cpsw_port *port;
> +       struct phy *phy;
> +       int i;
> +
> +       for (i = 0; i < common->port_num; i++) {
> +               port = &common->ports[i];
> +               phy = port->slave.serdes_phy;
> +               if (phy)
> +                       am65_cpsw_disable_phy(phy);
> +       }
> +}
> +
> +static int am65_cpsw_init_serdes_phy(struct device *dev, struct device_node *port_np,
> +                                    struct am65_cpsw_port *port)
> +{
> +       const char *name = "serdes-phy";
> +       struct phy *phy;
> +       int ret;
> +
> +       phy = devm_of_phy_get(dev, port_np, name);
> +       if (PTR_ERR(phy) == -ENODEV)
> +               return 0;
> +
> +       /* Serdes PHY exists. Store it. */

"phy" may be a different error here (e.g. -EPROBE_DEFER)...

> +       port->slave.serdes_phy = phy;
> +
> +       ret =  am65_cpsw_enable_phy(phy);

... so it will crash when dereferencing phy in phy_init().

I think you want to add an extra check above:

    if (IS_ERR(phy))
            return PTR_ERR(phy);

> +       if (ret < 0)
> +               goto err_phy;
> +
> +       return 0;
> +
> +err_phy:
> +       devm_phy_put(dev, phy);
> +       return ret;
> +}
> +
>  static void am65_cpsw_nuss_mac_config(struct phylink_config *config, unsigned int mode,
>                                       const struct phylink_link_state *state)
>  {
> @@ -1959,6 +2021,11 @@ static int am65_cpsw_nuss_init_slave_ports(struct am65_cpsw_common *common)

Right out of context we have:

                port->slave.ifphy = devm_of_phy_get(dev, port_np, NULL);
                if (IS_ERR(port->slave.ifphy)) {
                        ret = PTR_ERR(port->slave.ifphy);
                        dev_err(dev, "%pOF error retrieving port phy: %d\n",
                                port_np, ret);

So if there is only one PHY (named "serdes-phy") in DT, it will be
used for both ifphy and serdes_phy. Is that intentional?

>                         goto of_node_put;
>                 }
>
> +               /* Initialize the Serdes PHY for the port */
> +               ret = am65_cpsw_init_serdes_phy(dev, port_np, port);
> +               if (ret)
> +                       return ret;
> +
>                 port->slave.mac_only =
>                                 of_property_read_bool(port_np, "ti,mac-only");
>

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds