linux-kernel - [PATCH net-next v6 1/5] net: dsa: tag_yt921x: clarify priority and code fields

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Message-ID: <20260131021854.3405036-2-mmyangfl@gmail.com>
Date: Sat, 31 Jan 2026 10:18:47 +0800
From: David Yang <mmyangfl@...il.com>
To: netdev@...r.kernel.org
Cc: David Yang <mmyangfl@...il.com>,
	Andrew Lunn <andrew@...n.ch>,
	Vladimir Oltean <olteanv@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	Simon Horman <horms@...nel.org>,
	Russell King <linux@...linux.org.uk>,
	linux-kernel@...r.kernel.org
Subject: [PATCH net-next v6 1/5] net: dsa: tag_yt921x: clarify priority and code fields

Packet priority is part of the tag, and the priority and code fields are
used by tx and rx. Make revisions to reflect the facts.

Signed-off-by: David Yang <mmyangfl@...il.com>
---
 net/dsa/tag_yt921x.c | 83 ++++++++++++++++++++++++++++----------------
 1 file changed, 53 insertions(+), 30 deletions(-)

diff --git a/net/dsa/tag_yt921x.c b/net/dsa/tag_yt921x.c
index 6bbfd42dc5df..098863d491ff 100644
--- a/net/dsa/tag_yt921x.c
+++ b/net/dsa/tag_yt921x.c
@@ -14,11 +14,14 @@
  *     are conflicts somewhere and/or you want to change it for some reason.
  * Tag:
  *   2: VLAN Tag
- *   2: Rx Port
+ *   2:
  *     15b: Rx Port Valid
  *     14b-11b: Rx Port
- *     10b-0b: Cmd?
- *   2: Tx Port(s)
+ *     10b-8b: Tx/Rx Priority
+ *     7b: Tx/Rx Code Valid
+ *     6b-1b: Tx/Rx Code
+ *     0b: ? (unset)
+ *   2:
  *     15b: Tx Port(s) Valid
  *     10b-0b: Tx Port(s) Mask
  */
@@ -33,18 +36,30 @@
 
 #define YT921X_TAG_PORT_EN		BIT(15)
 #define YT921X_TAG_RX_PORT_M		GENMASK(14, 11)
-#define YT921X_TAG_RX_CMD_M		GENMASK(10, 0)
-#define  YT921X_TAG_RX_CMD(x)			FIELD_PREP(YT921X_TAG_RX_CMD_M, (x))
-#define  YT921X_TAG_RX_CMD_FORWARDED		0x80
-#define  YT921X_TAG_RX_CMD_UNK_UCAST		0xb2
-#define  YT921X_TAG_RX_CMD_UNK_MCAST		0xb4
-#define YT921X_TAG_TX_PORTS		GENMASK(10, 0)
+#define YT921X_TAG_PRIO_M		GENMASK(10, 8)
+#define  YT921X_TAG_PRIO(x)			FIELD_PREP(YT921X_TAG_PRIO_M, (x))
+#define YT921X_TAG_CODE_EN		BIT(7)
+#define YT921X_TAG_CODE_M		GENMASK(6, 1)
+#define  YT921X_TAG_CODE(x)			FIELD_PREP(YT921X_TAG_CODE_M, (x))
+#define YT921X_TAG_TX_PORTS_M		GENMASK(10, 0)
+#define  YT921X_TAG_TX_PORTS(x)			FIELD_PREP(YT921X_TAG_TX_PORTS_M, (x))
+
+/* Incomplete. Some are configurable via RMA_CTRL_CPU_CODE, the meaning of
+ * others remains unknown.
+ */
+enum yt921x_tag_code {
+	YT921X_TAG_CODE_FORWARD = 0,
+	YT921X_TAG_CODE_UNK_UCAST = 0x19,
+	YT921X_TAG_CODE_UNK_MCAST = 0x1a,
+	YT921X_TAG_CODE_PORT_COPY = 0x1b,
+	YT921X_TAG_CODE_FDB_COPY = 0x1c,
+};
 
 static struct sk_buff *
 yt921x_tag_xmit(struct sk_buff *skb, struct net_device *netdev)
 {
 	__be16 *tag;
-	u16 tx;
+	u16 ctrl;
 
 	skb_push(skb, YT921X_TAG_LEN);
 	dsa_alloc_etype_header(skb, YT921X_TAG_LEN);
@@ -55,9 +70,9 @@ yt921x_tag_xmit(struct sk_buff *skb, struct net_device *netdev)
 	/* VLAN tag unrelated when TX */
 	tag[1] = 0;
 	tag[2] = 0;
-	tx = FIELD_PREP(YT921X_TAG_TX_PORTS, dsa_xmit_port_mask(skb, netdev)) |
-	     YT921X_TAG_PORT_EN;
-	tag[3] = htons(tx);
+	ctrl = YT921X_TAG_TX_PORTS(dsa_xmit_port_mask(skb, netdev)) |
+	       YT921X_TAG_PORT_EN;
+	tag[3] = htons(ctrl);
 
 	return skb;
 }
@@ -67,7 +82,6 @@ yt921x_tag_rcv(struct sk_buff *skb, struct net_device *netdev)
 {
 	unsigned int port;
 	__be16 *tag;
-	u16 cmd;
 	u16 rx;
 
 	if (unlikely(!pskb_may_pull(skb, YT921X_TAG_LEN)))
@@ -98,23 +112,32 @@ yt921x_tag_rcv(struct sk_buff *skb, struct net_device *netdev)
 		return NULL;
 	}
 
-	cmd = FIELD_GET(YT921X_TAG_RX_CMD_M, rx);
-	switch (cmd) {
-	case YT921X_TAG_RX_CMD_FORWARDED:
-		/* Already forwarded by hardware */
-		dsa_default_offload_fwd_mark(skb);
-		break;
-	case YT921X_TAG_RX_CMD_UNK_UCAST:
-	case YT921X_TAG_RX_CMD_UNK_MCAST:
-		/* NOTE: hardware doesn't distinguish between TRAP (copy to CPU
-		 * only) and COPY (forward and copy to CPU). In order to perform
-		 * a soft switch, NEVER use COPY action in the switch driver.
-		 */
-		break;
-	default:
+	if (!(rx & YT921X_TAG_CODE_EN)) {
 		dev_warn_ratelimited(&netdev->dev,
-				     "Unexpected rx cmd 0x%02x\n", cmd);
-		break;
+				     "Tag code not enabled in rx packet\n");
+	} else {
+		u16 code = FIELD_GET(YT921X_TAG_CODE_M, rx);
+
+		switch (code) {
+		case YT921X_TAG_CODE_FORWARD:
+		case YT921X_TAG_CODE_PORT_COPY:
+		case YT921X_TAG_CODE_FDB_COPY:
+			/* Already forwarded by hardware */
+			dsa_default_offload_fwd_mark(skb);
+			break;
+		case YT921X_TAG_CODE_UNK_UCAST:
+		case YT921X_TAG_CODE_UNK_MCAST:
+			/* NOTE: hardware doesn't distinguish between TRAP (copy
+			 * to CPU only) and COPY (forward and copy to CPU). In
+			 * order to perform a soft switch, NEVER use COPY action
+			 * in the switch driver.
+			 */
+			break;
+		default:
+			dev_warn_ratelimited(&netdev->dev,
+					     "Unknown code 0x%02x\n", code);
+			break;
+		}
 	}
 
 	/* Remove YT921x tag and update checksum */
-- 
2.51.0