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// SPDX-License-Identifier: GPL-2.0+
/*
* DSA driver Special Tag support for MaxLinear GSW1xx switch chips
*
* Copyright (C) 2025 Daniel Golle <daniel@makrotopia.org>
* Copyright (C) 2023 - 2024 MaxLinear Inc.
*/
#include <linux/bitops.h>
#include <linux/etherdevice.h>
#include <linux/skbuff.h>
#include <net/dsa.h>
#include "tag.h"
/* To define the outgoing port and to discover the incoming port a special
* tag is used by the GSW1xx.
*
* Dest MAC Src MAC special TAG EtherType
* ...| 1 2 3 4 5 6 | 1 2 3 4 5 6 | 1 2 3 4 5 6 7 8 | 1 2 |...
* |<--------------->|
*/
#define GSW1XX_TAG_NAME "gsw1xx"
/* special tag header length (RX and TX) */
#define GSW1XX_HEADER_LEN 8
/* Word 0 = Ethertype -> 0x88C3 */
/* Word 1 */
#define GSW1XX_TX_PORT_MAP GENMASK(7, 0)
#define GSW1XX_TX_PORT_MAP_EN BIT(15)
#define GSW1XX_TX_CLASS_EN BIT(14)
#define GSW1XX_TX_TIME_STAMP_EN BIT(13)
#define GSW1XX_TX_LRN_DIS BIT(12)
#define GSW1XX_TX_CLASS GENMASK(11, 8)
/* special tag in RX path header */
/* Word 2 */
#define GSW1XX_RX_PORT_MAP GENMASK(15, 8)
static struct sk_buff *gsw1xx_tag_xmit(struct sk_buff *skb,
struct net_device *dev)
{
__be16 *gsw1xx_tag;
u16 tag;
/* provide additional space 'GSW1XX_HEADER_LEN' bytes */
skb_push(skb, GSW1XX_HEADER_LEN);
/* add space between MAC address and Ethertype */
dsa_alloc_etype_header(skb, GSW1XX_HEADER_LEN);
/* special tag ingress */
gsw1xx_tag = dsa_etype_header_pos_tx(skb);
gsw1xx_tag[0] = htons(ETH_P_MXLGSW);
tag = FIELD_PREP(GSW1XX_TX_PORT_MAP, dsa_xmit_port_mask(skb, dev)) |
GSW1XX_TX_PORT_MAP_EN | GSW1XX_TX_LRN_DIS;
gsw1xx_tag[1] = htons(tag);
gsw1xx_tag[2] = 0;
gsw1xx_tag[3] = 0;
return skb;
}
static struct sk_buff *gsw1xx_tag_rcv(struct sk_buff *skb,
struct net_device *dev)
{
int port;
__be16 *gsw1xx_tag;
if (unlikely(!pskb_may_pull(skb, GSW1XX_HEADER_LEN))) {
dev_warn_ratelimited(&dev->dev, "Dropping packet, cannot pull SKB\n");
return NULL;
}
gsw1xx_tag = dsa_etype_header_pos_rx(skb);
if (unlikely(ntohs(gsw1xx_tag[0]) != ETH_P_MXLGSW)) {
dev_warn_ratelimited(&dev->dev, "Dropping packet due to invalid special tag\n");
dev_warn_ratelimited(&dev->dev, "Tag: %8ph\n", gsw1xx_tag);
return NULL;
}
/* Get source port information */
port = FIELD_GET(GSW1XX_RX_PORT_MAP, ntohs(gsw1xx_tag[1]));
skb->dev = dsa_conduit_find_user(dev, 0, port);
if (!skb->dev) {
dev_warn_ratelimited(&dev->dev, "Dropping packet due to invalid source port\n");
dev_warn_ratelimited(&dev->dev, "Tag: %8ph\n", gsw1xx_tag);
return NULL;
}
/* remove the GSW1xx special tag between MAC addresses and the current
* ethertype field.
*/
skb_pull_rcsum(skb, GSW1XX_HEADER_LEN);
dsa_strip_etype_header(skb, GSW1XX_HEADER_LEN);
return skb;
}
static const struct dsa_device_ops gsw1xx_netdev_ops = {
.name = GSW1XX_TAG_NAME,
.proto = DSA_TAG_PROTO_MXL_GSW1XX,
.xmit = gsw1xx_tag_xmit,
.rcv = gsw1xx_tag_rcv,
.needed_headroom = GSW1XX_HEADER_LEN,
};
MODULE_DESCRIPTION("DSA tag driver for MaxLinear GSW1xx 8 byte protocol");
MODULE_LICENSE("GPL");
MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_MXL_GSW1XX, GSW1XX_TAG_NAME);
module_dsa_tag_driver(gsw1xx_netdev_ops);
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