[RFC net-next 2/2] net: dsa: mt7530: trap packets from standalone ports to the CPU

[DENG Qingfang <dqfext@gmail.com>]

Consider the following bridge configuration, where bond0 is not
offloaded:

         +-- br0 --+
        / /   |     \
       / /    |      \
      /  |    |     bond0
     /   |    |     /   \
   swp0 swp1 swp2 swp3 swp4
     .        .       .
     .        .       .
     A        B       C

Ideally, when the switch receives a packet from swp3 or swp4, it should
forward the packet to the CPU, according to the port matrix and unknown
unicast flood settings.

But packet loss will happen if the destination address is at one of the
offloaded ports (swp0~2). For example, when client C sends a packet to
A, the FDB lookup will indicate that it should be forwarded to swp0, but
the port matrix of swp3 and swp4 is configured to only allow the CPU to
be its destination, so it is dropped.

MT7530's FDB has 8 filter IDs, but they are only available for shared
VLAN learning, and all VLAN-unaware ports use 0 as the default filter
ID.

Fortunately, MT7530 supports ACL, and the ACL action happens before the
FDB lookup. So we install an ACL rule which traps all packets to the
CPU, and enable it for standalone ports. This way, the packet loss can
be avoided.

Signed-off-by: DENG Qingfang <dqfext@gmail.com>
---
 drivers/net/dsa/mt7530.c | 28 ++++++++++++++++++++
 drivers/net/dsa/mt7530.h | 56 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 84 insertions(+)

diff --git a/drivers/net/dsa/mt7530.c b/drivers/net/dsa/mt7530.c
index 69f21b71614c..6b5c85446e6f 100644
--- a/drivers/net/dsa/mt7530.c
+++ b/drivers/net/dsa/mt7530.c
@@ -1228,6 +1228,8 @@ mt7530_port_bridge_join(struct dsa_switch *ds, int port,
 		mt7530_rmw(priv, MT7530_PCR_P(port),
 			   PCR_MATRIX_MASK, PCR_MATRIX(port_bitmap));
 	priv->ports[port].pm |= PCR_MATRIX(port_bitmap);
+	/* Don't trap frames to the CPU port */
+	mt7530_clear(priv, MT7530_PCR_P(port), PORT_ACL_EN);
 
 	mutex_unlock(&priv->reg_mutex);
 
@@ -1328,6 +1330,8 @@ mt7530_port_bridge_leave(struct dsa_switch *ds, int port,
 		mt7530_rmw(priv, MT7530_PCR_P(port), PCR_MATRIX_MASK,
 			   PCR_MATRIX(BIT(MT7530_CPU_PORT)));
 	priv->ports[port].pm = PCR_MATRIX(BIT(MT7530_CPU_PORT));
+	/* Trap all frames to the CPU port */
+	mt7530_set(priv, MT7530_PCR_P(port), PORT_ACL_EN);
 
 	mutex_unlock(&priv->reg_mutex);
 }
@@ -2037,6 +2041,24 @@ mt7530_setup_mdio(struct mt7530_priv *priv)
 	return ret;
 }
 
+static void
+mt7530_setup_acl(struct mt7530_priv *priv)
+{
+	u32 action;
+
+	/* Set ACL pattern mask to 0 to match unconditionally */
+	mt7530_write(priv, MT7530_VAWD1, 0);
+	mt7530_write(priv, MT7530_VAWD2, 0);
+	mt7530_vlan_cmd(priv, MT7530_VTCR_WR_ACL_MASK, 0);
+
+	/* Set ACL action to forward frames to the CPU port */
+	action = ACL_PORT_EN | ACL_PORT(BIT(MT7530_CPU_PORT)) |
+		 ACL_EG_TAG(MT7530_VLAN_EG_CONSISTENT);
+	mt7530_write(priv, MT7530_VAWD1, action);
+	mt7530_write(priv, MT7530_VAWD2, 0);
+	mt7530_vlan_cmd(priv, MT7530_VTCR_WR_ACL_ACTION, 0);
+}
+
 static int
 mt7530_setup(struct dsa_switch *ds)
 {
@@ -2133,6 +2155,8 @@ mt7530_setup(struct dsa_switch *ds)
 
 			/* Disable learning by default on all user ports */
 			mt7530_set(priv, MT7530_PSC_P(i), SA_DIS);
+			/* Trap all frames to the CPU port */
+			mt7530_set(priv, MT7530_PCR_P(i), PORT_ACL_EN);
 		}
 		/* Enable consistent egress tag */
 		mt7530_rmw(priv, MT7530_PVC_P(i), PVC_EG_TAG_MASK,
@@ -2300,6 +2324,8 @@ mt7531_setup(struct dsa_switch *ds)
 
 			/* Disable learning by default on all user ports */
 			mt7530_set(priv, MT7530_PSC_P(i), SA_DIS);
+			/* Trap all frames to the CPU port */
+			mt7530_set(priv, MT7530_PCR_P(i), PORT_ACL_EN);
 		}
 
 		/* Enable consistent egress tag */
@@ -3005,6 +3031,8 @@ mt753x_setup(struct dsa_switch *ds)
 	if (ret)
 		return ret;
 
+	mt7530_setup_acl(priv);
+
 	ret = mt7530_setup_irq(priv);
 	if (ret)
 		return ret;
diff --git a/drivers/net/dsa/mt7530.h b/drivers/net/dsa/mt7530.h
index b19b389ff10a..10cb278d7c36 100644
--- a/drivers/net/dsa/mt7530.h
+++ b/drivers/net/dsa/mt7530.h
@@ -137,6 +137,15 @@ enum mt7530_vlan_cmd {
 	 */
 	MT7530_VTCR_RD_VID = 0,
 	MT7530_VTCR_WR_VID = 1,
+	/* Read/Write the specified ACL rule pattern */
+	MT7530_VTCR_RD_ACL_PATTERN = 4,
+	MT7530_VTCR_WR_ACL_PATTERN = 5,
+	/* Read/Write the specified ACL rule mask */
+	MT7530_VTCR_RD_ACL_MASK = 8,
+	MT7530_VTCR_WR_ACL_MASK = 9,
+	/* Read/Write the specified ACL rule action */
+	MT7530_VTCR_RD_ACL_ACTION = 10,
+	MT7530_VTCR_WR_ACL_ACTION = 11,
 };
 
 /* Register for setup vlan and acl write data */
@@ -153,6 +162,35 @@ enum mt7530_vlan_cmd {
 #define  PORT_MEM_SHFT			16
 #define  PORT_MEM_MASK			0xff
 
+/* ACL rule pattern */
+#define  BIT_CMP(x)			(((x) & 0xffff) << 16)
+#define  CMP_PAT(x)			((x) & 0xffff)
+
+/* ACL rule action */
+#define  ACL_MANG			BIT(29)
+#define  ACL_INT_EN			BIT(28)
+#define  ACL_CNT_EN			BIT(27)
+#define  ACL_CNT_IDX(x)			(((x) & 0x7) << 24)
+#define  VLAN_PORT_EN			BIT(23)
+#define  DA_SWAP			BIT(22)
+#define  SA_SWAP			BIT(21)
+#define  PPP_RM				BIT(20)
+#define  LKY_VLAN			BIT(19)
+#define  ACL_EG_TAG(x)			(((x) & 0x7) << 16)
+#define  ACL_PORT(x)			(((x) & 0xff) << 8)
+#define  ACL_PORT_EN			BIT(7)
+#define  PRI_USER(x)			(((x) & 0x7) << 4)
+#define  ACL_MIR_EN			BIT(3)
+#define  ACL_PORT_FW(x)			((x) & 0x7)
+
+enum mt7530_to_cpu_port_fw {
+	PORT_FW_DEFAULT,
+	PORT_FW_EXCLUDE_CPU = 4,
+	PORT_FW_INCLUDE_CPU,
+	PORT_FW_CPU_ONLY,
+	PORT_FW_DROP,
+};
+
 #define MT7530_VAWD2			0x98
 /* Egress Tag Control */
 #define  ETAG_CTRL_P(p, x)		(((x) & 0x3) << ((p) << 1))
@@ -164,6 +202,23 @@ enum mt7530_vlan_egress_attr {
 	MT7530_VLAN_EGRESS_STACK = 3,
 };
 
+/* ACL rule pattern */
+#define  ACL_TABLE_EN			BIT(19)
+#define  OFST_TP(x)			(((x) & 0x7) << 16)
+#define  ACL_SP(x)			(((x) & 0xff) << 8)
+#define  WORD_OFST(x)			(((x) & 0x7f) << 1)
+#define  CMP_SEL			BIT(0)
+
+enum mt7530_acl_offset_type {
+	MT7530_ACL_MAC_HEADER,
+	MT7530_ACL_L2_PAYLOAD,
+	MT7530_ACL_IP_HEADER,
+	MT7530_ACL_IP_DATAGRAM,
+	MT7530_ACL_TCP_UDP_HEADER,
+	MT7530_ACL_TCP_UDP_DATAGRAM,
+	MT7530_ACL_IPV6_HEADER,
+};
+
 /* Register for address age control */
 #define MT7530_AAC			0xa0
 /* Disable ageing */
@@ -192,6 +247,7 @@ enum mt7530_stp_state {
 
 /* Register for port control */
 #define MT7530_PCR_P(x)			(0x2004 + ((x) * 0x100))
+#define  PORT_ACL_EN			BIT(10)
 #define  PORT_TX_MIR			BIT(9)
 #define  PORT_RX_MIR			BIT(8)
 #define  PORT_VLAN(x)			((x) & 0x3)
-- 
2.25.1