Re: [PATCH net 1/2] net: dsa: realtek: rtl8365mb: use IVL in VLAN 0

["Alvin Šipraga" <alvin.sipraga@analog.com>]

On Wed, Nov 04, 2026 at 09:25:13AM +0100, Stijn Cleynhens wrote:
> DSA installs the FDB and MDB entries of standalone ports and of
> VLAN-unaware bridges with VID 0, and the driver writes them with
> Independent VLAN Learning. No bridge VLAN sets up the VLAN4k entry of
> VID 0 though, and it defaults to Shared VLAN Learning, so the switch
> looks up and learns frames classified to VID 0 by FID. Lookups never hit
> the IVL-keyed static entries, and a learned entry for the same MAC sits
> alongside the static one.
> 
> Set up VID 0 with IVL, like every other VLAN the driver programs.
> 
> On its own this has no visible effect: standalone ports do not learn and
> the driver does not control host flooding, so the unused static entries
> only meant that traffic was flooded to the CPU. The next patch, which
> moves VLAN-unaware bridges onto VID 0, depends on it.

Yes, all this makes sense. I actually remember doing basically the same
thing back when I was working on this, but it seems not to have survived
the final work by Luiz. It would be good to get his input on why. I
think he asked me at some point, but I couldn't remember, and so he
rightfully dropped it. But I could be wrong.

> 
> Fixes: 336e3e4a1ab3 ("net: dsa: realtek: rtl8365mb: add FDB support")
> Signed-off-by: Stijn Cleynhens <stijncleynhens@gmail.com>
> ---
>  drivers/net/dsa/realtek/rtl8365mb_main.c |  8 ++++++
>  drivers/net/dsa/realtek/rtl8365mb_vlan.c | 31 ++++++++++++++++++++++++
>  drivers/net/dsa/realtek/rtl8365mb_vlan.h |  1 +
>  3 files changed, 40 insertions(+)
> 
> diff --git a/drivers/net/dsa/realtek/rtl8365mb_main.c b/drivers/net/dsa/realtek/rtl8365mb_main.c
> index da06f952a..b90e46c16 100644
> --- a/drivers/net/dsa/realtek/rtl8365mb_main.c
> +++ b/drivers/net/dsa/realtek/rtl8365mb_main.c
> @@ -2232,6 +2232,14 @@ static int rtl8365mb_vlan_setup(struct dsa_switch *ds)
>  		}
>  	}
>  
> +	mutex_lock(&priv->vlan_lock);
> +	ret = rtl8365mb_vlan_4k_setup_neutral(priv);
> +	mutex_unlock(&priv->vlan_lock);

So I'm not sure I like this function being added to the vlan.c
library. Semantically it makes more sense to me for the main.c driver to
actually call rtl8365mb_vlan4k_port_add() for each port, so as to
explicitly say: "all ports are, one way or another, members of this
neutral VLAN". Then you would get IVL automatically.

But that API uses a struct switchdev_obj, which would be a bit crude to
construct here... So I see why you did it like this.

If you could give it a second thought and see if there's a neater way,
that would be nice. But either way I think this is fine, so:

Reviewed-by: Alvin Šipraga <alvin.sipraga@analog.com>

> +	if (ret) {
> +		dev_err(priv->dev, "Failed to set up VLAN 0\n");
> +		return ret;
> +	}
> +
>  	/* VLAN is always enabled. */
>  	ret = regmap_update_bits(priv->map, RTL8365MB_VLAN_CTRL_REG,
>  				 RTL8365MB_VLAN_CTRL_EN_MASK,
> diff --git a/drivers/net/dsa/realtek/rtl8365mb_vlan.c b/drivers/net/dsa/realtek/rtl8365mb_vlan.c
> index 8d49ffadc..58948e76f 100644
> --- a/drivers/net/dsa/realtek/rtl8365mb_vlan.c
> +++ b/drivers/net/dsa/realtek/rtl8365mb_vlan.c
> @@ -322,6 +322,37 @@ rtl8365mb_vlan_4k_port_set(struct dsa_switch *ds, int port,
>  	return 0;
>  }
>  
> +/*
> + * rtl8365mb_vlan_4k_setup_neutral() - Use IVL in the neutral VLAN
> + * @priv: realtek_priv pointer
> + *
> + * Untagged frames of standalone ports and of ports in a VLAN-unaware bridge
> + * are classified to VID 0, the VID of the neutral PVID. No bridge VLAN sets
> + * up its VLAN4k entry, which by default uses Shared VLAN Learning, so the
> + * switch would learn these frames by FID while the driver installs its FDB
> + * and MDB entries for VID 0 with Independent VLAN Learning. Use IVL in VID 0
> + * as in every other VLAN.
> + *
> + * Context: Can sleep. Must be called with &priv->vlan_lock held.
> + * Takes and releases &priv->map_lock.
> + * Return: 0 on success, or a negative error code on failure.
> + */
> +int rtl8365mb_vlan_4k_setup_neutral(struct realtek_priv *priv)
> +{
> +	struct rtl8365mb_vlan4k vlan4k = {0};
> +	int ret;
> +
> +	lockdep_assert_held(&priv->vlan_lock);
> +
> +	ret = rtl8365mb_vlan_4k_read(priv, 0, &vlan4k);
> +	if (ret)
> +		return ret;
> +
> +	vlan4k.ivl_en = true;
> +
> +	return rtl8365mb_vlan_4k_write(priv, &vlan4k);
> +}
> +
>  /*
>   * rtl8365mb_vlan_4k_port_add() - Add a port to a VLAN 4K table entry
>   * @ds: dsa switch instance
> diff --git a/drivers/net/dsa/realtek/rtl8365mb_vlan.h b/drivers/net/dsa/realtek/rtl8365mb_vlan.h
> index 27a526b61..809034009 100644
> --- a/drivers/net/dsa/realtek/rtl8365mb_vlan.h
> +++ b/drivers/net/dsa/realtek/rtl8365mb_vlan.h
> @@ -28,6 +28,7 @@ int
>  rtl8365mb_vlan_port_set_framefilter(struct realtek_priv *priv,
>  				    int port,
>  				    enum rtl8365mb_frame_ingress frame_type);
> +int rtl8365mb_vlan_4k_setup_neutral(struct realtek_priv *priv);
>  int rtl8365mb_vlan_4k_port_add(struct dsa_switch *ds, int port,
>  			       const struct switchdev_obj_port_vlan *vlan,
>  			       struct netlink_ext_ack *extack);
> -- 
> 2.56.0
>