[PATCH net-next v4 02/14] net: dsa: tag_brcm: add support for legacy FCS tags
From: Álvaro Fernández Rojas <hidden>
Date: 2025-06-14 08:00:08
Also in:
lkml
Subsystem:
broadcom b53/sf2 ethernet switch driver, networking [dsa], networking [general], the rest · Maintainers:
Florian Fainelli, Jonas Gorski, Andrew Lunn, Vladimir Oltean, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
Add support for legacy Broadcom FCS tags, which are similar to DSA_TAG_PROTO_BRCM_LEGACY. BCM5325 and BCM5365 switches require including the original FCS value and length, as opposed to BCM63xx switches. Adding the original FCS value and length to DSA_TAG_PROTO_BRCM_LEGACY would impact performance of BCM63xx switches, so it's better to create a new tag. Signed-off-by: Álvaro Fernández Rojas <redacted> --- include/net/dsa.h | 2 ++ net/dsa/Kconfig | 16 ++++++++-- net/dsa/tag_brcm.c | 73 +++++++++++++++++++++++++++++++++++++++++++++- 3 files changed, 88 insertions(+), 3 deletions(-) v4: fix line length warning. v3: fix warnings: - Improve Kconfig description. - Use __le32 type. - Use crc32_le() instead of crc32(). v2: replace swab32 with cpu_to_le32.
diff --git a/include/net/dsa.h b/include/net/dsa.h
index 55e2d97f247e..d73ea0880066 100644
--- a/include/net/dsa.h
+++ b/include/net/dsa.h@@ -54,11 +54,13 @@ struct tc_action; #define DSA_TAG_PROTO_RZN1_A5PSW_VALUE 26 #define DSA_TAG_PROTO_LAN937X_VALUE 27 #define DSA_TAG_PROTO_VSC73XX_8021Q_VALUE 28 +#define DSA_TAG_PROTO_BRCM_LEGACY_FCS_VALUE 29 enum dsa_tag_protocol { DSA_TAG_PROTO_NONE = DSA_TAG_PROTO_NONE_VALUE, DSA_TAG_PROTO_BRCM = DSA_TAG_PROTO_BRCM_VALUE, DSA_TAG_PROTO_BRCM_LEGACY = DSA_TAG_PROTO_BRCM_LEGACY_VALUE, + DSA_TAG_PROTO_BRCM_LEGACY_FCS = DSA_TAG_PROTO_BRCM_LEGACY_FCS_VALUE, DSA_TAG_PROTO_BRCM_PREPEND = DSA_TAG_PROTO_BRCM_PREPEND_VALUE, DSA_TAG_PROTO_DSA = DSA_TAG_PROTO_DSA_VALUE, DSA_TAG_PROTO_EDSA = DSA_TAG_PROTO_EDSA_VALUE,
diff --git a/net/dsa/Kconfig b/net/dsa/Kconfig
index 2dfe9063613f..869cbe57162f 100644
--- a/net/dsa/Kconfig
+++ b/net/dsa/Kconfig@@ -42,12 +42,24 @@ config NET_DSA_TAG_BRCM Broadcom switches which place the tag after the MAC source address. config NET_DSA_TAG_BRCM_LEGACY - tristate "Tag driver for Broadcom legacy switches using in-frame headers" + tristate "Tag driver for BCM63xx legacy switches using in-frame headers" select NET_DSA_TAG_BRCM_COMMON help Say Y if you want to enable support for tagging frames for the - Broadcom legacy switches which place the tag after the MAC source + BCM63xx legacy switches which place the tag after the MAC source address. + This tag is used in BCM63xx legacy switches which work without the + original FCS and length before the tag insertion. + +config NET_DSA_TAG_BRCM_LEGACY_FCS + tristate "Tag driver for BCM53xx legacy switches using in-frame headers" + select NET_DSA_TAG_BRCM_COMMON + help + Say Y if you want to enable support for tagging frames for the + BCM53xx legacy switches which place the tag after the MAC source + address. + This tag is used in BCM53xx legacy switches which expect original + FCS and length before the tag insertion to be present. config NET_DSA_TAG_BRCM_PREPEND tristate "Tag driver for Broadcom switches using prepended headers"
diff --git a/net/dsa/tag_brcm.c b/net/dsa/tag_brcm.c
index 9f4b0bcd95cd..26bb657ceac3 100644
--- a/net/dsa/tag_brcm.c
+++ b/net/dsa/tag_brcm.c@@ -15,6 +15,7 @@ #define BRCM_NAME "brcm" #define BRCM_LEGACY_NAME "brcm-legacy" +#define BRCM_LEGACY_FCS_NAME "brcm-legacy-fcs" #define BRCM_PREPEND_NAME "brcm-prepend" /* Legacy Broadcom tag (6 bytes) */
@@ -32,6 +33,10 @@ #define BRCM_LEG_MULTICAST (1 << 5) #define BRCM_LEG_EGRESS (2 << 5) #define BRCM_LEG_INGRESS (3 << 5) +#define BRCM_LEG_LEN_HI(x) (((x) >> 8) & 0x7) + +/* 4th byte in the tag */ +#define BRCM_LEG_LEN_LO(x) ((x) & 0xff) /* 6th byte in the tag */ #define BRCM_LEG_PORT_ID (0xf)
@@ -212,7 +217,8 @@ DSA_TAG_DRIVER(brcm_netdev_ops); MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_BRCM, BRCM_NAME); #endif -#if IS_ENABLED(CONFIG_NET_DSA_TAG_BRCM_LEGACY) +#if IS_ENABLED(CONFIG_NET_DSA_TAG_BRCM_LEGACY) || \ + IS_ENABLED(CONFIG_NET_DSA_TAG_BRCM_LEGACY_FCS) static struct sk_buff *brcm_leg_tag_rcv(struct sk_buff *skb, struct net_device *dev) {
@@ -244,7 +250,9 @@ static struct sk_buff *brcm_leg_tag_rcv(struct sk_buff *skb, return skb; } +#endif /* CONFIG_NET_DSA_TAG_BRCM_LEGACY || CONFIG_NET_DSA_TAG_BRCM_LEGACY_FCS */ +#if IS_ENABLED(CONFIG_NET_DSA_TAG_BRCM_LEGACY) static struct sk_buff *brcm_leg_tag_xmit(struct sk_buff *skb, struct net_device *dev) {
@@ -294,6 +302,66 @@ DSA_TAG_DRIVER(brcm_legacy_netdev_ops); MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_BRCM_LEGACY, BRCM_LEGACY_NAME); #endif /* CONFIG_NET_DSA_TAG_BRCM_LEGACY */ +#if IS_ENABLED(CONFIG_NET_DSA_TAG_BRCM_LEGACY_FCS) +static struct sk_buff *brcm_leg_fcs_tag_xmit(struct sk_buff *skb, + struct net_device *dev) +{ + struct dsa_port *dp = dsa_user_to_port(dev); + unsigned int fcs_len; + __le32 fcs_val; + u8 *brcm_tag; + + /* The Ethernet switch we are interfaced with needs packets to be at + * least 64 bytes (including FCS) otherwise they will be discarded when + * they enter the switch port logic. When Broadcom tags are enabled, we + * need to make sure that packets are at least 70 bytes (including FCS + * and tag) because the length verification is done after the Broadcom + * tag is stripped off the ingress packet. + * + * Let dsa_user_xmit() free the SKB. + */ + if (__skb_put_padto(skb, ETH_ZLEN + BRCM_LEG_TAG_LEN, false)) + return NULL; + + fcs_len = skb->len; + fcs_val = cpu_to_le32(crc32_le(~0, skb->data, fcs_len) ^ ~0); + + skb_push(skb, BRCM_LEG_TAG_LEN); + + dsa_alloc_etype_header(skb, BRCM_LEG_TAG_LEN); + + brcm_tag = skb->data + 2 * ETH_ALEN; + + /* Broadcom tag type */ + brcm_tag[0] = BRCM_LEG_TYPE_HI; + brcm_tag[1] = BRCM_LEG_TYPE_LO; + + /* Broadcom tag value */ + brcm_tag[2] = BRCM_LEG_EGRESS | BRCM_LEG_LEN_HI(fcs_len); + brcm_tag[3] = BRCM_LEG_LEN_LO(fcs_len); + brcm_tag[4] = 0; + brcm_tag[5] = dp->index & BRCM_LEG_PORT_ID; + + /* Original FCS value */ + if (__skb_pad(skb, ETH_FCS_LEN, false)) + return NULL; + skb_put_data(skb, &fcs_val, ETH_FCS_LEN); + + return skb; +} + +static const struct dsa_device_ops brcm_legacy_fcs_netdev_ops = { + .name = BRCM_LEGACY_FCS_NAME, + .proto = DSA_TAG_PROTO_BRCM_LEGACY_FCS, + .xmit = brcm_leg_fcs_tag_xmit, + .rcv = brcm_leg_tag_rcv, + .needed_headroom = BRCM_LEG_TAG_LEN, +}; + +DSA_TAG_DRIVER(brcm_legacy_fcs_netdev_ops); +MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_BRCM_LEGACY_FCS, BRCM_LEGACY_FCS_NAME); +#endif /* CONFIG_NET_DSA_TAG_BRCM_LEGACY_FCS */ + #if IS_ENABLED(CONFIG_NET_DSA_TAG_BRCM_PREPEND) static struct sk_buff *brcm_tag_xmit_prepend(struct sk_buff *skb, struct net_device *dev)
@@ -328,6 +396,9 @@ static struct dsa_tag_driver *dsa_tag_driver_array[] = { #if IS_ENABLED(CONFIG_NET_DSA_TAG_BRCM_LEGACY) &DSA_TAG_DRIVER_NAME(brcm_legacy_netdev_ops), #endif +#if IS_ENABLED(CONFIG_NET_DSA_TAG_BRCM_LEGACY_FCS) + &DSA_TAG_DRIVER_NAME(brcm_legacy_fcs_netdev_ops), +#endif #if IS_ENABLED(CONFIG_NET_DSA_TAG_BRCM_PREPEND) &DSA_TAG_DRIVER_NAME(brcm_prepend_netdev_ops), #endif
--
2.39.5