net: dsa: sja1105: Add support for port mirroring

Amazingly, of all features, this does not require a switch reset.

Tested with:

tc qdisc add dev swp2 clsact
tc filter add dev swp2 ingress matchall skip_sw \
	action mirred egress mirror dev swp3
tc filter show dev swp2 ingress
tc filter del dev swp2 ingress pref 49152

Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/sja1105/sja1105_main.c

@@ -382,8 +382,8 @@ static int sja1105_init_l2_forwarding_params(struct sja1105_private *priv)
 static int sja1105_init_general_params(struct sja1105_private *priv)
 {
 	struct sja1105_general_params_entry default_general_params = {
-		/* Disallow dynamic changing of the mirror port */
-		.mirr_ptacu = 0,
+		/* Allow dynamic changing of the mirror port */
+		.mirr_ptacu = true,
 		.switchid = priv->ds->index,
 		/* Priority queue for link-local management frames
 		 * (both ingress to and egress from CPU - PTP, STP etc)
@@ -403,8 +403,8 @@ static int sja1105_init_general_params(struct sja1105_private *priv)
 		 * by installing a temporary 'management route'
 		 */
 		.host_port = dsa_upstream_port(priv->ds, 0),
-		/* Same as host port */
-		.mirr_port = dsa_upstream_port(priv->ds, 0),
+		/* Default to an invalid value */
+		.mirr_port = SJA1105_NUM_PORTS,
 		/* Link-local traffic received on casc_port will be forwarded
 		 * to host_port without embedding the source port and device ID
 		 * info in the destination MAC address (presumably because it
@@ -2069,6 +2069,84 @@ static int sja1105_port_setup_tc(struct dsa_switch *ds, int port,
 	}
 }
 
+/* We have a single mirror (@to) port, but can configure ingress and egress
+ * mirroring on all other (@from) ports.
+ * We need to allow mirroring rules only as long as the @to port is always the
+ * same, and we need to unset the @to port from mirr_port only when there is no
+ * mirroring rule that references it.
+ */
+static int sja1105_mirror_apply(struct sja1105_private *priv, int from, int to,
+				bool ingress, bool enabled)
+{
+	struct sja1105_general_params_entry *general_params;
+	struct sja1105_mac_config_entry *mac;
+	struct sja1105_table *table;
+	bool already_enabled;
+	u64 new_mirr_port;
+	int rc;
+
+	table = &priv->static_config.tables[BLK_IDX_GENERAL_PARAMS];
+	general_params = table->entries;
+
+	mac = priv->static_config.tables[BLK_IDX_MAC_CONFIG].entries;
+
+	already_enabled = (general_params->mirr_port != SJA1105_NUM_PORTS);
+	if (already_enabled && enabled && general_params->mirr_port != to) {
+		dev_err(priv->ds->dev,
+			"Delete mirroring rules towards port %llu first\n",
+			general_params->mirr_port);
+		return -EBUSY;
+	}
+
+	new_mirr_port = to;
+	if (!enabled) {
+		bool keep = false;
+		int port;
+
+		/* Anybody still referencing mirr_port? */
+		for (port = 0; port < SJA1105_NUM_PORTS; port++) {
+			if (mac[port].ing_mirr || mac[port].egr_mirr) {
+				keep = true;
+				break;
+			}
+		}
+		/* Unset already_enabled for next time */
+		if (!keep)
+			new_mirr_port = SJA1105_NUM_PORTS;
+	}
+	if (new_mirr_port != general_params->mirr_port) {
+		general_params->mirr_port = new_mirr_port;
+
+		rc = sja1105_dynamic_config_write(priv, BLK_IDX_GENERAL_PARAMS,
+						  0, general_params, true);
+		if (rc < 0)
+			return rc;
+	}
+
+	if (ingress)
+		mac[from].ing_mirr = enabled;
+	else
+		mac[from].egr_mirr = enabled;
+
+	return sja1105_dynamic_config_write(priv, BLK_IDX_MAC_CONFIG, from,
+					    &mac[from], true);
+}
+
+static int sja1105_mirror_add(struct dsa_switch *ds, int port,
+			      struct dsa_mall_mirror_tc_entry *mirror,
+			      bool ingress)
+{
+	return sja1105_mirror_apply(ds->priv, port, mirror->to_local_port,
+				    ingress, true);
+}
+
+static void sja1105_mirror_del(struct dsa_switch *ds, int port,
+			       struct dsa_mall_mirror_tc_entry *mirror)
+{
+	sja1105_mirror_apply(ds->priv, port, mirror->to_local_port,
+			     mirror->ingress, false);
+}
+
 static const struct dsa_switch_ops sja1105_switch_ops = {
 	.get_tag_protocol	= sja1105_get_tag_protocol,
 	.setup			= sja1105_setup,
@@ -2102,6 +2180,8 @@ static const struct dsa_switch_ops sja1105_switch_ops = {
 	.port_rxtstamp		= sja1105_port_rxtstamp,
 	.port_txtstamp		= sja1105_port_txtstamp,
 	.port_setup_tc		= sja1105_port_setup_tc,
+	.port_mirror_add	= sja1105_mirror_add,
+	.port_mirror_del	= sja1105_mirror_del,
 };
 
 static int sja1105_check_device_id(struct sja1105_private *priv)