openwrt/target/linux/lantiq/patches-5.10/0703-net-lantiq-enable-jumbo-frames-on-GSWIP.patch

From 24a43ae2ac0ea06c474b1c80dc75651294d49321 Mon Sep 17 00:00:00 2001
From: Thomas Nixon <tom@tomn.co.uk>
Date: Sat, 2 Oct 2021 00:48:05 +0100
Subject: [PATCH 2/2] net: lantiq: enable jumbo frames on GSWIP

This enables non-standard MTUs on a per-port basis, with the overall
frame size set based on the CPU port.

When the MTU is not changed, this should have no effect.

Long packets crash the switch with MTUs of greater than 2526, so the
maximum is limited for now.

Signed-off-by: Thomas Nixon <tom@tomn.co.uk>
---
 drivers/net/dsa/lantiq_gswip.c | 46 +++++++++++++++++++++++++++++++---
 1 file changed, 42 insertions(+), 4 deletions(-)

--- a/drivers/net/dsa/lantiq_gswip.c
+++ b/drivers/net/dsa/lantiq_gswip.c
@@ -238,6 +238,11 @@
 
 #define XRX200_GPHY_FW_ALIGN	(16 * 1024)
 
+/* maximum packet size supported by the switch; in theory this should be 9600,
+ * but long packets currently cause lock-ups with an MTU of over 2526
+ */
+#define GSWIP_MAX_PACKET_LENGTH	2556
+
 struct gswip_hw_info {
 	int max_ports;
 	int cpu_port;
@@ -851,10 +856,6 @@ static int gswip_setup(struct dsa_switch
 	gswip_switch_mask(priv, 0, GSWIP_PCE_PCTRL_0_INGRESS,
 			  GSWIP_PCE_PCTRL_0p(cpu_port));
 
-	gswip_switch_mask(priv, 0, GSWIP_MAC_CTRL_2_MLEN,
-			  GSWIP_MAC_CTRL_2p(cpu_port));
-	gswip_switch_w(priv, VLAN_ETH_FRAME_LEN + 8 + ETH_FCS_LEN,
-		       GSWIP_MAC_FLEN);
 	gswip_switch_mask(priv, 0, GSWIP_BM_QUEUE_GCTRL_GL_MOD,
 			  GSWIP_BM_QUEUE_GCTRL);
 
@@ -871,6 +872,8 @@ static int gswip_setup(struct dsa_switch
 		return err;
 	}
 
+	ds->mtu_enforcement_ingress = true;
+
 	gswip_port_enable(ds, cpu_port, NULL);
 	return 0;
 }
@@ -1433,6 +1436,39 @@ static int gswip_port_fdb_dump(struct ds
 	return 0;
 }
 
+static int gswip_port_max_mtu(struct dsa_switch *ds, int port)
+{
+	/* includes 8 bytes for special header */
+	return GSWIP_MAX_PACKET_LENGTH - VLAN_ETH_HLEN - ETH_FCS_LEN;
+}
+
+static int gswip_port_change_mtu(struct dsa_switch *ds, int port, int new_mtu)
+{
+	struct gswip_priv *priv = ds->priv;
+	int cpu_port = priv->hw_info->cpu_port;
+
+	/* cpu port always has maximum mtu of user ports, so use it to set
+	 * switch frame size, including 8 byte special header
+	 */
+	if (port == cpu_port) {
+		new_mtu += 8;
+		gswip_switch_w(priv, VLAN_ETH_HLEN + new_mtu + ETH_FCS_LEN,
+			       GSWIP_MAC_FLEN);
+	}
+
+	/* enable MLEN for ports with non-standard MTUs, including the special
+	 * header on the CPU port added above
+	 */
+	if (new_mtu != ETH_DATA_LEN)
+		gswip_switch_mask(priv, 0, GSWIP_MAC_CTRL_2_MLEN,
+				  GSWIP_MAC_CTRL_2p(port));
+	else
+		gswip_switch_mask(priv, GSWIP_MAC_CTRL_2_MLEN, 0,
+				  GSWIP_MAC_CTRL_2p(port));
+
+	return 0;
+}
+
 static void gswip_phylink_validate(struct dsa_switch *ds, int port,
 				   unsigned long *supported,
 				   struct phylink_link_state *state)
@@ -1776,6 +1812,8 @@ static const struct dsa_switch_ops gswip
 	.port_fdb_add		= gswip_port_fdb_add,
 	.port_fdb_del		= gswip_port_fdb_del,
 	.port_fdb_dump		= gswip_port_fdb_dump,
+	.port_change_mtu	= gswip_port_change_mtu,
+	.port_max_mtu		= gswip_port_max_mtu,
 	.phylink_validate	= gswip_phylink_validate,
 	.phylink_mac_config	= gswip_phylink_mac_config,
 	.phylink_mac_link_down	= gswip_phylink_mac_link_down,