net: dsa: add tag format for MxL862xx switches

Add proprietary special tag format for the MaxLinear MXL862xx family of
switches. While using the same Ethertype as MaxLinear's GSW1xx switches,
the actual tag format differs significantly, hence we need a dedicated
tag driver for that.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>
Link: https://patch.msgid.link/c64e6ddb6c93a4fac39f9ab9b2d8bf551a2b118d.1770433307.git.daniel@makrotopia.org
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

diff --git a/MAINTAINERS b/MAINTAINERS
index 608caa55d7d22b638f6333e4e851237d6966f209..0c9b34eda5acb35fd7d01abf698377c56736a86e 100644 (file)
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -15631,6 +15631,7 @@ M:      Daniel Golle <daniel@makrotopia.org>
 L:     netdev@vger.kernel.org
 S:     Maintained
 F:     Documentation/devicetree/bindings/net/dsa/maxlinear,mxl862xx.yaml
+F:     net/dsa/tag_mxl862xx.c
 
 MCAN DEVICE DRIVER
 M:     Markus Schneider-Pargmann <msp@baylibre.com>

diff --git a/include/net/dsa.h b/include/net/dsa.h
index 65699036579874fe287aeb65c54006d8d50d2f37..6c17446f3dcc29682e07a70362bae8d8fa6233b0 100644 (file)
--- a/include/net/dsa.h
+++ b/include/net/dsa.h
@@ -57,6 +57,7 @@ struct tc_action;
 #define DSA_TAG_PROTO_BRCM_LEGACY_FCS_VALUE    29
 #define DSA_TAG_PROTO_YT921X_VALUE             30
 #define DSA_TAG_PROTO_MXL_GSW1XX_VALUE         31
+#define DSA_TAG_PROTO_MXL862_VALUE             32
 
 enum dsa_tag_protocol {
        DSA_TAG_PROTO_NONE              = DSA_TAG_PROTO_NONE_VALUE,
@@ -91,6 +92,7 @@ enum dsa_tag_protocol {
        DSA_TAG_PROTO_VSC73XX_8021Q     = DSA_TAG_PROTO_VSC73XX_8021Q_VALUE,
        DSA_TAG_PROTO_YT921X            = DSA_TAG_PROTO_YT921X_VALUE,
        DSA_TAG_PROTO_MXL_GSW1XX        = DSA_TAG_PROTO_MXL_GSW1XX_VALUE,
+       DSA_TAG_PROTO_MXL862            = DSA_TAG_PROTO_MXL862_VALUE,
 };
 
 struct dsa_switch;

diff --git a/net/dsa/Kconfig b/net/dsa/Kconfig
index f86b30742122fc32e964080a4bb5b9f7a756fa99..5ed8c704636dd7fc6e35ea0835f8e510eecc3d79 100644 (file)
--- a/net/dsa/Kconfig
+++ b/net/dsa/Kconfig
@@ -104,6 +104,13 @@ config NET_DSA_TAG_MTK
          Say Y or M if you want to enable support for tagging frames for
          Mediatek switches.
 
+config NET_DSA_TAG_MXL_862XX
+       tristate "Tag driver for MaxLinear MxL862xx switches"
+       help
+         Say Y or M if you want to enable support for tagging frames for the
+         MaxLinear MxL86252 and MxL86282 switches using their native 8-byte
+         tagging protocol.
+
 config NET_DSA_TAG_MXL_GSW1XX
        tristate "Tag driver for MaxLinear GSW1xx switches"
        help

diff --git a/net/dsa/Makefile b/net/dsa/Makefile
index 42d173f5a7013ae7539eb441a872b0fc5d8229cd..bf7247759a64a037d10956f2658dbe286f4223f2 100644 (file)
--- a/net/dsa/Makefile
+++ b/net/dsa/Makefile
@@ -28,6 +28,7 @@ obj-$(CONFIG_NET_DSA_TAG_HELLCREEK) += tag_hellcreek.o
 obj-$(CONFIG_NET_DSA_TAG_KSZ) += tag_ksz.o
 obj-$(CONFIG_NET_DSA_TAG_LAN9303) += tag_lan9303.o
 obj-$(CONFIG_NET_DSA_TAG_MTK) += tag_mtk.o
+obj-$(CONFIG_NET_DSA_TAG_MXL_862XX) += tag_mxl862xx.o
 obj-$(CONFIG_NET_DSA_TAG_MXL_GSW1XX) += tag_mxl-gsw1xx.o
 obj-$(CONFIG_NET_DSA_TAG_NONE) += tag_none.o
 obj-$(CONFIG_NET_DSA_TAG_OCELOT) += tag_ocelot.o

diff --git a/net/dsa/tag_mxl862xx.c b/net/dsa/tag_mxl862xx.c
new file mode 100644 (file)
index 0000000..01f2158
--- /dev/null
+++ b/net/dsa/tag_mxl862xx.c
@@ -0,0 +1,110 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * DSA Special Tag for MaxLinear 862xx switch chips
+ *
+ * Copyright (C) 2025 Daniel Golle <daniel@makrotopia.org>
+ * Copyright (C) 2024 MaxLinear Inc.
+ */
+
+#include <linux/bitops.h>
+#include <linux/etherdevice.h>
+#include <linux/skbuff.h>
+#include <net/dsa.h>
+#include "tag.h"
+
+#define MXL862_NAME    "mxl862xx"
+
+#define MXL862_HEADER_LEN      8
+
+/* Word 0 -> EtherType */
+
+/* Word 2 */
+#define MXL862_SUBIF_ID                GENMASK(4, 0)
+
+/* Word 3 */
+#define MXL862_IGP_EGP         GENMASK(3, 0)
+
+static struct sk_buff *mxl862_tag_xmit(struct sk_buff *skb,
+                                      struct net_device *dev)
+{
+       struct dsa_port *dp = dsa_user_to_port(dev);
+       struct dsa_port *cpu_dp = dp->cpu_dp;
+       unsigned int cpu_port, sub_interface;
+       __be16 *mxl862_tag;
+
+       cpu_port = cpu_dp->index;
+
+       /* target port sub-interface ID relative to the CPU port */
+       sub_interface = dp->index + 16 - cpu_port;
+
+       /* provide additional space 'MXL862_HEADER_LEN' bytes */
+       skb_push(skb, MXL862_HEADER_LEN);
+
+       /* shift MAC address to the beginning of the enlarged buffer,
+        * releasing the space required for DSA tag (between MAC address and
+        * Ethertype)
+        */
+       dsa_alloc_etype_header(skb, MXL862_HEADER_LEN);
+
+       /* special tag ingress (from the perspective of the switch) */
+       mxl862_tag = dsa_etype_header_pos_tx(skb);
+       mxl862_tag[0] = htons(ETH_P_MXLGSW);
+       mxl862_tag[1] = 0;
+       mxl862_tag[2] = htons(FIELD_PREP(MXL862_SUBIF_ID, sub_interface));
+       mxl862_tag[3] = htons(FIELD_PREP(MXL862_IGP_EGP, cpu_port));
+
+       return skb;
+}
+
+static struct sk_buff *mxl862_tag_rcv(struct sk_buff *skb,
+                                     struct net_device *dev)
+{
+       __be16 *mxl862_tag;
+       int port;
+
+       if (unlikely(!pskb_may_pull(skb, MXL862_HEADER_LEN))) {
+               dev_warn_ratelimited(&dev->dev, "Cannot pull SKB, packet dropped\n");
+               return NULL;
+       }
+
+       mxl862_tag = dsa_etype_header_pos_rx(skb);
+
+       if (unlikely(mxl862_tag[0] != htons(ETH_P_MXLGSW))) {
+               dev_warn_ratelimited(&dev->dev,
+                                    "Invalid special tag marker, packet dropped, tag: %8ph\n",
+                                    mxl862_tag);
+               return NULL;
+       }
+
+       /* Get source port information */
+       port = FIELD_GET(MXL862_IGP_EGP, ntohs(mxl862_tag[3]));
+       skb->dev = dsa_conduit_find_user(dev, 0, port);
+       if (unlikely(!skb->dev)) {
+               dev_warn_ratelimited(&dev->dev,
+                                    "Invalid source port, packet dropped, tag: %8ph\n",
+                                    mxl862_tag);
+               return NULL;
+       }
+
+       /* remove the MxL862xx special tag between the MAC addresses and the
+        * current ethertype field.
+        */
+       skb_pull_rcsum(skb, MXL862_HEADER_LEN);
+       dsa_strip_etype_header(skb, MXL862_HEADER_LEN);
+
+       return skb;
+}
+
+static const struct dsa_device_ops mxl862_netdev_ops = {
+       .name = MXL862_NAME,
+       .proto = DSA_TAG_PROTO_MXL862,
+       .xmit = mxl862_tag_xmit,
+       .rcv = mxl862_tag_rcv,
+       .needed_headroom = MXL862_HEADER_LEN,
+};
+
+MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_MXL862, MXL862_NAME);
+MODULE_DESCRIPTION("DSA tag driver for MaxLinear MxL862xx switches");
+MODULE_LICENSE("GPL");
+
+module_dsa_tag_driver(mxl862_netdev_ops);