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Message-Id: <20250530155618.273567-3-noltari@gmail.com>
Date: Fri, 30 May 2025 17:56:17 +0200
From: Álvaro Fernández Rojas <noltari@...il.com>
To: jonas.gorski@...il.com,
florian.fainelli@...adcom.com,
andrew@...n.ch,
olteanv@...il.com,
davem@...emloft.net,
edumazet@...gle.com,
kuba@...nel.org,
pabeni@...hat.com,
horms@...nel.org,
netdev@...r.kernel.org,
linux-kernel@...r.kernel.org,
dgcbueu@...il.com
Cc: Álvaro Fernández Rojas <noltari@...il.com>
Subject: [PATCH] net: dsa: tag_brcm: add support for legacy FCS tags
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 <noltari@...il.com>
---
include/net/dsa.h | 2 ++
net/dsa/Kconfig | 8 ++++++
net/dsa/tag_brcm.c | 71 +++++++++++++++++++++++++++++++++++++++++++++-
3 files changed, 80 insertions(+), 1 deletion(-)
diff --git a/include/net/dsa.h b/include/net/dsa.h
index 55e2d97f247eb..d73ea08800660 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 2dfe9063613fe..e6696e8212cf3 100644
--- a/net/dsa/Kconfig
+++ b/net/dsa/Kconfig
@@ -49,6 +49,14 @@ config NET_DSA_TAG_BRCM_LEGACY
Broadcom legacy switches which place the tag after the MAC source
address.
+config NET_DSA_TAG_BRCM_LEGACY_FCS
+ tristate "Tag driver for Broadcom legacy switches using in-frame headers, FCS and length"
+ 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
+ address and require the original FCS and length.
+
config NET_DSA_TAG_BRCM_PREPEND
tristate "Tag driver for Broadcom switches using prepended headers"
select NET_DSA_TAG_BRCM_COMMON
diff --git a/net/dsa/tag_brcm.c b/net/dsa/tag_brcm.c
index 9f4b0bcd95cde..7bf4bde2d8672 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 +302,64 @@ 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;
+ u32 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 = swab32(crc32(~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 */
+ 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 +394,9 @@ 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
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