--- /dev/null
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Motorcomm YT921x Switch Extended CPU Port Tagging
+ *
+ * Copyright (c) 2025 David Yang <mmyangfl@gmail.com>
+ *
+ * +----+----+-------+-----+----+---------
+ * | DA | SA | TagET | Tag | ET | Payload ...
+ * +----+----+-------+-----+----+---------
+ * 6 6 2 6 2 N
+ *
+ * Tag Ethertype: CPU_TAG_TPID_TPID (default: ETH_P_YT921X = 0x9988)
+ * * Hardcoded for the moment, but still configurable. Discuss it if there
+ * are conflicts somewhere and/or you want to change it for some reason.
+ * Tag:
+ * 2: VLAN Tag
+ * 2: Rx Port
+ * 15b: Rx Port Valid
+ * 14b-11b: Rx Port
+ * 10b-0b: Cmd?
+ * 2: Tx Port(s)
+ * 15b: Tx Port(s) Valid
+ * 10b-0b: Tx Port(s) Mask
+ */
+
+#include <linux/etherdevice.h>
+
+#include "tag.h"
+
+#define YT921X_TAG_NAME "yt921x"
+
+#define YT921X_TAG_LEN 8
+
+#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_M GENMASK(10, 0)
+#define YT921X_TAG_TX_PORTn(port) BIT(port)
+
+static struct sk_buff *
+yt921x_tag_xmit(struct sk_buff *skb, struct net_device *netdev)
+{
+ struct dsa_port *dp = dsa_user_to_port(netdev);
+ unsigned int port = dp->index;
+ __be16 *tag;
+ u16 tx;
+
+ skb_push(skb, YT921X_TAG_LEN);
+ dsa_alloc_etype_header(skb, YT921X_TAG_LEN);
+
+ tag = dsa_etype_header_pos_tx(skb);
+
+ tag[0] = htons(ETH_P_YT921X);
+ /* VLAN tag unrelated when TX */
+ tag[1] = 0;
+ tag[2] = 0;
+ tx = YT921X_TAG_PORT_EN | YT921X_TAG_TX_PORTn(port);
+ tag[3] = htons(tx);
+
+ return skb;
+}
+
+static struct sk_buff *
+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)))
+ return NULL;
+
+ tag = dsa_etype_header_pos_rx(skb);
+
+ if (unlikely(tag[0] != htons(ETH_P_YT921X))) {
+ dev_warn_ratelimited(&netdev->dev,
+ "Unexpected EtherType 0x%04x\n",
+ ntohs(tag[0]));
+ return NULL;
+ }
+
+ /* Locate which port this is coming from */
+ rx = ntohs(tag[2]);
+ if (unlikely((rx & YT921X_TAG_PORT_EN) == 0)) {
+ dev_warn_ratelimited(&netdev->dev,
+ "Unexpected rx tag 0x%04x\n", rx);
+ return NULL;
+ }
+
+ port = FIELD_GET(YT921X_TAG_RX_PORT_M, rx);
+ skb->dev = dsa_conduit_find_user(netdev, 0, port);
+ if (unlikely(!skb->dev)) {
+ dev_warn_ratelimited(&netdev->dev,
+ "Couldn't decode source port %u\n", port);
+ 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:
+ dev_warn_ratelimited(&netdev->dev,
+ "Unexpected rx cmd 0x%02x\n", cmd);
+ break;
+ }
+
+ /* Remove YT921x tag and update checksum */
+ skb_pull_rcsum(skb, YT921X_TAG_LEN);
+ dsa_strip_etype_header(skb, YT921X_TAG_LEN);
+
+ return skb;
+}
+
+static const struct dsa_device_ops yt921x_netdev_ops = {
+ .name = YT921X_TAG_NAME,
+ .proto = DSA_TAG_PROTO_YT921X,
+ .xmit = yt921x_tag_xmit,
+ .rcv = yt921x_tag_rcv,
+ .needed_headroom = YT921X_TAG_LEN,
+};
+
+MODULE_DESCRIPTION("DSA tag driver for Motorcomm YT921x switches");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_YT921X, YT921X_TAG_NAME);
+
+module_dsa_tag_driver(yt921x_netdev_ops);
projects / thirdparty / kernel / linux.git / commitdiff
