kernel: backport MediaTek jumbo frame support

Allow MTU up to 2026 on mediatek, ramips/mt7621 targets.

Signed-off-by: DENG Qingfang <dqfext@gmail.com>
Tested-by: Arınç ÜNAL <arinc.unal@arinc9.com>
Tested-by: Stijn Tintel <stijn@linux-ipv6.be>

1 files changed, 112 insertions, 0 deletions

diff --git a/target/linux/generic/backport-5.10/762-v5.11-net-dsa-mt7530-support-setting-MTU.patch b/target/linux/generic/backport-5.10/762-v5.11-net-dsa-mt7530-support-setting-MTU.patch
new file mode 100644
index 0000000000..eb487cdfb5
--- /dev/null
+++ b/target/linux/generic/backport-5.10/762-v5.11-net-dsa-mt7530-support-setting-MTU.patch
@@ -0,0 +1,112 @@
+From 9470174e7581e75a8ebd78964997314dfc2e706c Mon Sep 17 00:00:00 2001
+From: DENG Qingfang <dqfext@gmail.com>
+Date: Tue, 3 Nov 2020 13:06:18 +0800
+Subject: [PATCH] net: dsa: mt7530: support setting MTU
+
+MT7530/7531 has a global RX packet length register, which can be used
+to set MTU.
+
+Supported packet length values are 1522 (1518 if untagged), 1536,
+1552, and multiple of 1024 (from 2048 to 15360).
+
+Signed-off-by: DENG Qingfang <dqfext@gmail.com>
+Link: https://lore.kernel.org/r/20201103050618.11419-1-dqfext@gmail.com
+Signed-off-by: Jakub Kicinski <kuba@kernel.org>
+---
+ drivers/net/dsa/mt7530.c | 49 ++++++++++++++++++++++++++++++++++++++++
+ drivers/net/dsa/mt7530.h | 12 ++++++++++
+ 2 files changed, 61 insertions(+)
+
+--- a/drivers/net/dsa/mt7530.c
++++ b/drivers/net/dsa/mt7530.c
+@@ -1015,6 +1015,53 @@ mt7530_port_disable(struct dsa_switch *d
+ 	mutex_unlock(&priv->reg_mutex);
+ }
+ 
++static int
++mt7530_port_change_mtu(struct dsa_switch *ds, int port, int new_mtu)
++{
++	struct mt7530_priv *priv = ds->priv;
++	struct mii_bus *bus = priv->bus;
++	int length;
++	u32 val;
++
++	/* When a new MTU is set, DSA always set the CPU port's MTU to the
++	 * largest MTU of the slave ports. Because the switch only has a global
++	 * RX length register, only allowing CPU port here is enough.
++	 */
++	if (!dsa_is_cpu_port(ds, port))
++		return 0;
++
++	mutex_lock_nested(&bus->mdio_lock, MDIO_MUTEX_NESTED);
++
++	val = mt7530_mii_read(priv, MT7530_GMACCR);
++	val &= ~MAX_RX_PKT_LEN_MASK;
++
++	/* RX length also includes Ethernet header, MTK tag, and FCS length */
++	length = new_mtu + ETH_HLEN + MTK_HDR_LEN + ETH_FCS_LEN;
++	if (length <= 1522) {
++		val |= MAX_RX_PKT_LEN_1522;
++	} else if (length <= 1536) {
++		val |= MAX_RX_PKT_LEN_1536;
++	} else if (length <= 1552) {
++		val |= MAX_RX_PKT_LEN_1552;
++	} else {
++		val &= ~MAX_RX_JUMBO_MASK;
++		val |= MAX_RX_JUMBO(DIV_ROUND_UP(length, 1024));
++		val |= MAX_RX_PKT_LEN_JUMBO;
++	}
++
++	mt7530_mii_write(priv, MT7530_GMACCR, val);
++
++	mutex_unlock(&bus->mdio_lock);
++
++	return 0;
++}
++
++static int
++mt7530_port_max_mtu(struct dsa_switch *ds, int port)
++{
++	return MT7530_MAX_MTU;
++}
++
+ static void
+ mt7530_stp_state_set(struct dsa_switch *ds, int port, u8 state)
+ {
+@@ -2652,6 +2699,8 @@ static const struct dsa_switch_ops mt753
+ 	.get_sset_count		= mt7530_get_sset_count,
+ 	.port_enable		= mt7530_port_enable,
+ 	.port_disable		= mt7530_port_disable,
++	.port_change_mtu	= mt7530_port_change_mtu,
++	.port_max_mtu		= mt7530_port_max_mtu,
+ 	.port_stp_state_set	= mt7530_stp_state_set,
+ 	.port_bridge_join	= mt7530_port_bridge_join,
+ 	.port_bridge_leave	= mt7530_port_bridge_leave,
+--- a/drivers/net/dsa/mt7530.h
++++ b/drivers/net/dsa/mt7530.h
+@@ -11,6 +11,9 @@
+ #define MT7530_NUM_FDB_RECORDS		2048
+ #define MT7530_ALL_MEMBERS		0xff
+ 
++#define MTK_HDR_LEN	4
++#define MT7530_MAX_MTU	(15 * 1024 - ETH_HLEN - ETH_FCS_LEN - MTK_HDR_LEN)
++
+ enum mt753x_id {
+ 	ID_MT7530 = 0,
+ 	ID_MT7621 = 1,
+@@ -301,6 +304,15 @@ enum mt7530_vlan_port_attr {
+ #define MT7531_DBG_CNT(x)		(0x3018 + (x) * 0x100)
+ #define  MT7531_DIS_CLR			BIT(31)
+ 
++#define MT7530_GMACCR			0x30e0
++#define  MAX_RX_JUMBO(x)		((x) << 2)
++#define  MAX_RX_JUMBO_MASK		GENMASK(5, 2)
++#define  MAX_RX_PKT_LEN_MASK		GENMASK(1, 0)
++#define  MAX_RX_PKT_LEN_1522		0x0
++#define  MAX_RX_PKT_LEN_1536		0x1
++#define  MAX_RX_PKT_LEN_1552		0x2
++#define  MAX_RX_PKT_LEN_JUMBO		0x3
++
+ /* Register for MIB */
+ #define MT7530_PORT_MIB_COUNTER(x)	(0x4000 + (x) * 0x100)
+ #define MT7530_MIB_CCR			0x4fe0