netdev - RE: [PATCH 2/2] net: dsa: microchip: Provide Module 4 KSZ9477 errata (DS80000754C)

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Date: Fri, 25 Aug 2023 01:12:48 +0000
From: <Tristram.Ha@...rochip.com>
To: <lukma@...x.de>
CC: <andrew@...n.ch>, <f.fainelli@...il.com>, <olteanv@...il.com>,
	<davem@...emloft.net>, <edumazet@...gle.com>, <kuba@...nel.org>,
	<Woojung.Huh@...rochip.com>, <pabeni@...hat.com>, <netdev@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <UNGLinuxDriver@...rochip.com>
Subject: RE: [PATCH 2/2] net: dsa: microchip: Provide Module 4 KSZ9477 errata
 (DS80000754C)

> +static int ksz9477_errata(struct dsa_switch *ds)
> +{
> +       struct ksz_device *dev = ds->priv;
> +       u16 val;
> +       int p;
> +
> +       /* KSZ9477 Errata DS80000754C
> +        *
> +        * Module 4: Energy Efficient Ethernet (EEE) feature select must be
> +        * manually disabled
> +        *   The EEE feature is enabled by default, but it is not fully
> +        *   operational. It must be manually disabled through register
> +        *   controls. If not disabled, the PHY ports can auto-negotiate
> +        *   to enable EEE, and this feature can cause link drops when linked
> +        *   to another device supporting EEE.
> +        *
> +        *   Only PHY ports (dsa user) [0-4] need to have the EEE advertisement
> +        *   bits cleared.
> +        */
> +
> +       for (p = 0; p < ds->num_ports; p++) {
> +               if (!dsa_is_user_port(ds, p))
> +                       continue;
> +
> +               ksz9477_port_mmd_read(dev, p, MMD_DEVICE_ID_EEE_ADV,
> +                                     MMD_EEE_ADV, &val, 1);
> +
> +               pr_err("%s: PORT: %d val: 0x%x pc: %d\n", __func__, p, val,
> +                      ds->num_ports);
> +
> +               val &= ~(EEE_ADV_100MBIT | EEE_ADV_1GBIT);
> +               ksz9477_port_mmd_write(dev, p, MMD_DEVICE_ID_EEE_ADV,
> +                                      MMD_EEE_ADV, &val, 1);
> +       }
> +
> +       return 0;
> +}
> +
>  int ksz9477_setup(struct dsa_switch *ds)
>  {
>         struct ksz_device *dev = ds->priv;
> @@ -1157,7 +1195,7 @@ int ksz9477_setup(struct dsa_switch *ds)
>         /* enable global MIB counter freeze function */
>         ksz_cfg(dev, REG_SW_MAC_CTRL_6, SW_MIB_COUNTER_FREEZE, true);
> 
> -       return 0;
> +       return ksz9477_errata(ds);
>  }

I would prefer to execute the code in ksz9477_config_cpu_port(), as at
the end there is already a loop to do something to each port.  The check
to disable EEE or not should be dev->info->internal_phy[port], as one of
the user ports can be RGMII or SGMII, which does not have a PHY that can
be accessed inside the switch.

As the EEE register value is simply 6 it should be enough to just set
the register to zero.  If so we do not need to add back those
ksz9477_port_mmd_setup functions and just use ksz_pwrite16() to write to
the MMD register.