tag_mxl-gsw1xx.c

  1// SPDX-License-Identifier: GPL-2.0+
  2/*
  3 * DSA driver Special Tag support for MaxLinear GSW1xx switch chips
  4 *
  5 * Copyright (C) 2025 Daniel Golle <daniel@makrotopia.org>
  6 * Copyright (C) 2023 - 2024 MaxLinear Inc.
  7 */
  8
  9#include <linux/bitops.h>
 10#include <linux/etherdevice.h>
 11#include <linux/skbuff.h>
 12#include <net/dsa.h>
 13
 14#include "tag.h"
 15
 16/* To define the outgoing port and to discover the incoming port a special
 17 * tag is used by the GSW1xx.
 18 *
 19 *       Dest MAC       Src MAC    special TAG        EtherType
 20 * ...| 1 2 3 4 5 6 | 1 2 3 4 5 6 | 1 2 3 4 5 6 7 8 | 1 2 |...
 21 *                                |<--------------->|
 22 */
 23
 24#define GSW1XX_TAG_NAME		"gsw1xx"
 25
 26/* special tag header length (RX and TX) */
 27#define GSW1XX_HEADER_LEN		8
 28
 29/* Word 0 = Ethertype -> 0x88C3 */
 30
 31/* Word 1 */
 32#define GSW1XX_TX_PORT_MAP		GENMASK(7, 0)
 33#define GSW1XX_TX_PORT_MAP_EN		BIT(15)
 34#define GSW1XX_TX_CLASS_EN		BIT(14)
 35#define GSW1XX_TX_TIME_STAMP_EN		BIT(13)
 36#define GSW1XX_TX_LRN_DIS		BIT(12)
 37#define GSW1XX_TX_CLASS			GENMASK(11, 8)
 38
 39/* special tag in RX path header */
 40/* Word 2 */
 41#define GSW1XX_RX_PORT_MAP		GENMASK(15, 8)
 42
 43static struct sk_buff *gsw1xx_tag_xmit(struct sk_buff *skb,
 44				       struct net_device *dev)
 45{
 46	__be16 *gsw1xx_tag;
 47	u16 tag;
 48
 49	/* provide additional space 'GSW1XX_HEADER_LEN' bytes */
 50	skb_push(skb, GSW1XX_HEADER_LEN);
 51
 52	/* add space between MAC address and Ethertype */
 53	dsa_alloc_etype_header(skb, GSW1XX_HEADER_LEN);
 54
 55	/* special tag ingress */
 56	gsw1xx_tag = dsa_etype_header_pos_tx(skb);
 57	gsw1xx_tag[0] = htons(ETH_P_MXLGSW);
 58
 59	tag = FIELD_PREP(GSW1XX_TX_PORT_MAP, dsa_xmit_port_mask(skb, dev)) |
 60	      GSW1XX_TX_PORT_MAP_EN | GSW1XX_TX_LRN_DIS;
 61	gsw1xx_tag[1] = htons(tag);
 62	gsw1xx_tag[2] = 0;
 63	gsw1xx_tag[3] = 0;
 64
 65	return skb;
 66}
 67
 68static struct sk_buff *gsw1xx_tag_rcv(struct sk_buff *skb,
 69				      struct net_device *dev)
 70{
 71	int port;
 72	__be16 *gsw1xx_tag;
 73
 74	if (unlikely(!pskb_may_pull(skb, GSW1XX_HEADER_LEN))) {
 75		dev_warn_ratelimited(&dev->dev, "Dropping packet, cannot pull SKB\n");
 76		return NULL;
 77	}
 78
 79	gsw1xx_tag = dsa_etype_header_pos_rx(skb);
 80
 81	if (unlikely(ntohs(gsw1xx_tag[0]) != ETH_P_MXLGSW)) {
 82		dev_warn_ratelimited(&dev->dev, "Dropping packet due to invalid special tag\n");
 83		dev_warn_ratelimited(&dev->dev, "Tag: %8ph\n", gsw1xx_tag);
 84		return NULL;
 85	}
 86
 87	/* Get source port information */
 88	port = FIELD_GET(GSW1XX_RX_PORT_MAP, ntohs(gsw1xx_tag[1]));
 89	skb->dev = dsa_conduit_find_user(dev, 0, port);
 90	if (!skb->dev) {
 91		dev_warn_ratelimited(&dev->dev, "Dropping packet due to invalid source port\n");
 92		dev_warn_ratelimited(&dev->dev, "Tag: %8ph\n", gsw1xx_tag);
 93		return NULL;
 94	}
 95
 96	/* remove the GSW1xx special tag between MAC addresses and the current
 97	 * ethertype field.
 98	 */
 99	skb_pull_rcsum(skb, GSW1XX_HEADER_LEN);
100	dsa_strip_etype_header(skb, GSW1XX_HEADER_LEN);
101
102	return skb;
103}
104
105static const struct dsa_device_ops gsw1xx_netdev_ops = {
106	.name			= GSW1XX_TAG_NAME,
107	.proto			= DSA_TAG_PROTO_MXL_GSW1XX,
108	.xmit			= gsw1xx_tag_xmit,
109	.rcv			= gsw1xx_tag_rcv,
110	.needed_headroom	= GSW1XX_HEADER_LEN,
111};
112
113MODULE_DESCRIPTION("DSA tag driver for MaxLinear GSW1xx 8 byte protocol");
114MODULE_LICENSE("GPL");
115MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_MXL_GSW1XX, GSW1XX_TAG_NAME);
116
117module_dsa_tag_driver(gsw1xx_netdev_ops);