Re: [PATCH net-next v2 4/4] net: dsa: xrs700x: add HSR offloading support

+static int xrs700x_hsr_join(struct dsa_switch *ds, int port,
+			    struct net_device *hsr)
+{
+	unsigned int val = XRS_HSR_CFG_HSR_PRP;
+	struct dsa_port *partner = NULL, *dp;
+	struct xrs700x *priv = ds->priv;
+	struct net_device *slave;
+	enum hsr_version ver;
+	int ret;
+
+	ret = hsr_get_version(hsr, &ver);
+	if (ret)
+		return ret;
+
+	if (ver == HSR_V1)
+		val |= XRS_HSR_CFG_HSR;
+	else if (ver == PRP_V1)
+		val |= XRS_HSR_CFG_PRP;
+	else
+		return -EOPNOTSUPP;
+
+	dsa_hsr_foreach_port(dp, ds, hsr) {
+		partner = dp;
+	}
+
+	/* We can't enable redundancy on the switch until both
+	 * redundant ports have signed up.
+	 */
+	if (!partner)
+		return 0;
+
+	regmap_fields_write(priv->ps_forward, partner->index,
+			    XRS_PORT_DISABLED);
+	regmap_fields_write(priv->ps_forward, port, XRS_PORT_DISABLED);
+
+	regmap_write(priv->regmap, XRS_HSR_CFG(partner->index),
+		     val | XRS_HSR_CFG_LANID_A);
+	regmap_write(priv->regmap, XRS_HSR_CFG(port),
+		     val | XRS_HSR_CFG_LANID_B);
+
+	/* Clear bits for both redundant ports (HSR only) and the CPU port to
+	 * enable forwarding.
+	 */
+	val = GENMASK(ds->num_ports - 1, 0);
+	if (ver == HSR_V1) {
+		val &= ~BIT(partner->index);
+		val &= ~BIT(port);
+	}
+	val &= ~BIT(dsa_upstream_port(ds, port));
+	regmap_write(priv->regmap, XRS_PORT_FWD_MASK(partner->index), val);
+	regmap_write(priv->regmap, XRS_PORT_FWD_MASK(port), val);
+
+	regmap_fields_write(priv->ps_forward, partner->index,
+			    XRS_PORT_FORWARDING);
+	regmap_fields_write(priv->ps_forward, port, XRS_PORT_FORWARDING);
+
+	slave = dsa_to_port(ds, port)->slave;
+
+	slave->features |= NETIF_F_HW_HSR_TAG_INS | NETIF_F_HW_HSR_TAG_RM |
+			   NETIF_F_HW_HSR_FWD | NETIF_F_HW_HSR_DUP;
+
+	return 0;
+}