Merge branch 'dsa-realtek-add-rtl8_4t-tags'

Luiz Angelo Daros de Luca says:

====================
net: dsa: realtek: add rtl8_4t tag

This patch series adds support for rtl8_4t tag. It is a variant of
rtl8_4 tag, with identical values but placed at the end of the packet
(before CRC).

It forces checksum in software before adding the tag as those extra
bytes at the end of the packet would be summed together with the rest of
the payload. When the switch removes the tag before sending the packet
to the network, that checksum will not match.

It might be useful to diagnose or avoid checksum offload issues. With an
ethertype tag like rtl8_4, the cpu port ethernet driver must work with
cksum_start and chksum_offset to correctly calculate checksums. If not,
the checksum field will be broken (it will contain the fake ip header
sum).  In those cases, using 'rtl8_4t' might be an alternative way to
avoid checksum offload, either using runtime or device-tree property.

Regards,

Luiz

v4-v5)
- tags in alphabetical order in dsa_port.yaml
- remove ret var from rtl8365mb_change_tag_protocol
- Comment typos fixes

v3-v4)
- added rtl8_4 and rtl8_4t to dsa_port.yaml
- removed generic considerations about checksum problems with DSA tags.
  They belong to Documentation/networking/dsa/dsa.rst

v2-v3)
- updated tag documentation (file header)
- do not remove position and format from rtl8365mb_cpu
- reinstate cpu to rtl8365mb
- moved rtl8365mb_change_tag_protocol after rtl8365mb_cpu_config
- do not modify rtl8365mb_cpu_config() logic
- remove cpu arg from rtl8365mb_cpu_config(); get it from priv
- dropped tag_protocol from rtl8365mb. It is now derived from
  cpu->position.
- init cpu struct before dsa_register as default tag must be already
  defined before dsa_register()
- fix formatting issues

v1-v2)
- remove mention to tail tagger, use trailing tagger.
- use void* instead of char* for pointing to tag beginning
- use memcpy to avoid problems with unaligned tags
- calculate checksum if it still pending
- keep in-use tag protocol in memory instead of reading from switch
  register
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/devicetree/bindings/net/dsa/dsa-port.yaml

@@ -51,6 +51,8 @@ properties:
       - edsa
       - ocelot
       - ocelot-8021q
+      - rtl8_4
+      - rtl8_4t
       - seville
 
   phy-handle: true

drivers/net/dsa/realtek/rtl8365mb.c

@@ -566,6 +566,7 @@ struct rtl8365mb_port {
  * @chip_ver: chip silicon revision
  * @port_mask: mask of all ports
  * @learn_limit_max: maximum number of L2 addresses the chip can learn
+ * @cpu: CPU tagging and CPU port configuration for this chip
  * @mib_lock: prevent concurrent reads of MIB counters
  * @ports: per-port data
  * @jam_table: chip-specific initialization jam table
@@ -580,6 +581,7 @@ struct rtl8365mb {
 	u32 chip_ver;
 	u32 port_mask;
 	u32 learn_limit_max;
+	struct rtl8365mb_cpu cpu;
 	struct mutex mib_lock;
 	struct rtl8365mb_port ports[RTL8365MB_MAX_NUM_PORTS];
 	const struct rtl8365mb_jam_tbl_entry *jam_table;
@@ -782,6 +784,16 @@ static enum dsa_tag_protocol
 rtl8365mb_get_tag_protocol(struct dsa_switch *ds, int port,
 			   enum dsa_tag_protocol mp)
 {
+	struct realtek_priv *priv = ds->priv;
+	struct rtl8365mb_cpu *cpu;
+	struct rtl8365mb *mb;
+
+	mb = priv->chip_data;
+	cpu = &mb->cpu;
+
+	if (cpu->position == RTL8365MB_CPU_POS_BEFORE_CRC)
+		return DSA_TAG_PROTO_RTL8_4T;
+
 	return DSA_TAG_PROTO_RTL8_4;
 }
 
@@ -1737,8 +1749,10 @@ static void rtl8365mb_irq_teardown(struct realtek_priv *priv)
 	}
 }
 
-static int rtl8365mb_cpu_config(struct realtek_priv *priv, const struct rtl8365mb_cpu *cpu)
+static int rtl8365mb_cpu_config(struct realtek_priv *priv)
 {
+	struct rtl8365mb *mb = priv->chip_data;
+	struct rtl8365mb_cpu *cpu = &mb->cpu;
 	u32 val;
 	int ret;
 
@@ -1764,6 +1778,37 @@ static int rtl8365mb_cpu_config(struct realtek_priv *priv, const struct rtl8365m
 	return 0;
 }
 
+static int rtl8365mb_change_tag_protocol(struct dsa_switch *ds, int cpu_index,
+					 enum dsa_tag_protocol proto)
+{
+	struct realtek_priv *priv = ds->priv;
+	struct rtl8365mb_cpu *cpu;
+	struct rtl8365mb *mb;
+
+	mb = priv->chip_data;
+	cpu = &mb->cpu;
+
+	switch (proto) {
+	case DSA_TAG_PROTO_RTL8_4:
+		cpu->format = RTL8365MB_CPU_FORMAT_8BYTES;
+		cpu->position = RTL8365MB_CPU_POS_AFTER_SA;
+		break;
+	case DSA_TAG_PROTO_RTL8_4T:
+		cpu->format = RTL8365MB_CPU_FORMAT_8BYTES;
+		cpu->position = RTL8365MB_CPU_POS_BEFORE_CRC;
+		break;
+	/* The switch also supports a 4-byte format, similar to rtl4a but with
+	 * the same 0x04 8-bit version and probably 8-bit port source/dest.
+	 * There is no public doc about it. Not supported yet and it will probably
+	 * never be.
+	 */
+	default:
+		return -EPROTONOSUPPORT;
+	}
+
+	return rtl8365mb_cpu_config(priv);
+}
+
 static int rtl8365mb_switch_init(struct realtek_priv *priv)
 {
 	struct rtl8365mb *mb = priv->chip_data;
@@ -1810,13 +1855,14 @@ static int rtl8365mb_reset_chip(struct realtek_priv *priv)
 static int rtl8365mb_setup(struct dsa_switch *ds)
 {
 	struct realtek_priv *priv = ds->priv;
-	struct rtl8365mb_cpu cpu = {0};
+	struct rtl8365mb_cpu *cpu;
 	struct dsa_port *cpu_dp;
 	struct rtl8365mb *mb;
 	int ret;
 	int i;
 
 	mb = priv->chip_data;
+	cpu = &mb->cpu;
 
 	ret = rtl8365mb_reset_chip(priv);
 	if (ret) {
@@ -1839,21 +1885,14 @@ static int rtl8365mb_setup(struct dsa_switch *ds)
 		dev_info(priv->dev, "no interrupt support\n");
 
 	/* Configure CPU tagging */
-	cpu.trap_port = RTL8365MB_MAX_NUM_PORTS;
 	dsa_switch_for_each_cpu_port(cpu_dp, priv->ds) {
-		cpu.mask |= BIT(cpu_dp->index);
+		cpu->mask |= BIT(cpu_dp->index);
 
-		if (cpu.trap_port == RTL8365MB_MAX_NUM_PORTS)
-			cpu.trap_port = cpu_dp->index;
+		if (cpu->trap_port == RTL8365MB_MAX_NUM_PORTS)
+			cpu->trap_port = cpu_dp->index;
 	}
-
-	cpu.enable = cpu.mask > 0;
-	cpu.insert = RTL8365MB_CPU_INSERT_TO_ALL;
-	cpu.position = RTL8365MB_CPU_POS_AFTER_SA;
-	cpu.rx_length = RTL8365MB_CPU_RXLEN_64BYTES;
-	cpu.format = RTL8365MB_CPU_FORMAT_8BYTES;
-
-	ret = rtl8365mb_cpu_config(priv, &cpu);
+	cpu->enable = cpu->mask > 0;
+	ret = rtl8365mb_cpu_config(priv);
 	if (ret)
 		goto out_teardown_irq;
 
@@ -1865,7 +1904,7 @@ static int rtl8365mb_setup(struct dsa_switch *ds)
 			continue;
 
 		/* Forward only to the CPU */
-		ret = rtl8365mb_port_set_isolation(priv, i, cpu.mask);
+		ret = rtl8365mb_port_set_isolation(priv, i, cpu->mask);
 		if (ret)
 			goto out_teardown_irq;
 
@@ -1995,6 +2034,12 @@ static int rtl8365mb_detect(struct realtek_priv *priv)
 		mb->jam_table = rtl8365mb_init_jam_8365mb_vc;
 		mb->jam_size = ARRAY_SIZE(rtl8365mb_init_jam_8365mb_vc);
 
+		mb->cpu.trap_port = RTL8365MB_MAX_NUM_PORTS;
+		mb->cpu.insert = RTL8365MB_CPU_INSERT_TO_ALL;
+		mb->cpu.position = RTL8365MB_CPU_POS_AFTER_SA;
+		mb->cpu.rx_length = RTL8365MB_CPU_RXLEN_64BYTES;
+		mb->cpu.format = RTL8365MB_CPU_FORMAT_8BYTES;
+
 		break;
 	default:
 		dev_err(priv->dev,
@@ -2008,6 +2053,7 @@ static int rtl8365mb_detect(struct realtek_priv *priv)
 
 static const struct dsa_switch_ops rtl8365mb_switch_ops_smi = {
 	.get_tag_protocol = rtl8365mb_get_tag_protocol,
+	.change_tag_protocol = rtl8365mb_change_tag_protocol,
 	.setup = rtl8365mb_setup,
 	.teardown = rtl8365mb_teardown,
 	.phylink_get_caps = rtl8365mb_phylink_get_caps,
@@ -2026,6 +2072,7 @@ static const struct dsa_switch_ops rtl8365mb_switch_ops_smi = {
 
 static const struct dsa_switch_ops rtl8365mb_switch_ops_mdio = {
 	.get_tag_protocol = rtl8365mb_get_tag_protocol,
+	.change_tag_protocol = rtl8365mb_change_tag_protocol,
 	.setup = rtl8365mb_setup,
 	.teardown = rtl8365mb_teardown,
 	.phylink_get_caps = rtl8365mb_phylink_get_caps,

include/net/dsa.h

@@ -52,6 +52,7 @@ struct phylink_link_state;
 #define DSA_TAG_PROTO_BRCM_LEGACY_VALUE		22
 #define DSA_TAG_PROTO_SJA1110_VALUE		23
 #define DSA_TAG_PROTO_RTL8_4_VALUE		24
+#define DSA_TAG_PROTO_RTL8_4T_VALUE		25
 
 enum dsa_tag_protocol {
 	DSA_TAG_PROTO_NONE		= DSA_TAG_PROTO_NONE_VALUE,
@@ -79,6 +80,7 @@ enum dsa_tag_protocol {
 	DSA_TAG_PROTO_SEVILLE		= DSA_TAG_PROTO_SEVILLE_VALUE,
 	DSA_TAG_PROTO_SJA1110		= DSA_TAG_PROTO_SJA1110_VALUE,
 	DSA_TAG_PROTO_RTL8_4		= DSA_TAG_PROTO_RTL8_4_VALUE,
+	DSA_TAG_PROTO_RTL8_4T		= DSA_TAG_PROTO_RTL8_4T_VALUE,
 };
 
 struct dsa_switch;

net/dsa/tag_rtl8_4.c

@@ -7,13 +7,8 @@
  * NOTE: Currently only supports protocol "4" found in the RTL8365MB, hence
  * named tag_rtl8_4.
  *
- * This tag header has the following format:
+ * This tag has the following format:
  *
- *  -------------------------------------------
- *  | MAC DA | MAC SA | 8 byte tag | Type | ...
- *  -------------------------------------------
- *     _______________/            \______________________________________
- *    /                                                                   \
  *  0                                  7|8                                 15
  *  |-----------------------------------+-----------------------------------|---
  *  |                               (16-bit)                                | ^
@@ -58,6 +53,24 @@
  *    TX/RX      | TX (switch->CPU): port number the packet was received on
  *               | RX (CPU->switch): forwarding port mask (if ALLOW=0)
  *               |                   allowance port mask (if ALLOW=1)
+ *
+ * The tag can be positioned before Ethertype, using tag "rtl8_4":
+ *
+ *  +--------+--------+------------+------+-----
+ *  | MAC DA | MAC SA | 8 byte tag | Type | ...
+ *  +--------+--------+------------+------+-----
+ *
+ * The tag can also appear between the end of the payload and before the CRC,
+ * using tag "rtl8_4t":
+ *
+ * +--------+--------+------+-----+---------+------------+-----+
+ * | MAC DA | MAC SA | TYPE | ... | payload | 8-byte tag | CRC |
+ * +--------+--------+------+-----+---------+------------+-----+
+ *
+ * The added bytes after the payload will break most checksums, either in
+ * software or hardware. To avoid this issue, if the checksum is still pending,
+ * this tagger checksums the packet in software before adding the tag.
+ *
  */
 
 #include <linux/bitfield.h>
@@ -84,87 +97,133 @@
 #define RTL8_4_TX			GENMASK(3, 0)
 #define RTL8_4_RX			GENMASK(10, 0)
 
-static struct sk_buff *rtl8_4_tag_xmit(struct sk_buff *skb,
-				       struct net_device *dev)
+static void rtl8_4_write_tag(struct sk_buff *skb, struct net_device *dev,
+			     void *tag)
 {
 	struct dsa_port *dp = dsa_slave_to_port(dev);
-	__be16 *tag;
-
-	skb_push(skb, RTL8_4_TAG_LEN);
-
-	dsa_alloc_etype_header(skb, RTL8_4_TAG_LEN);
-	tag = dsa_etype_header_pos_tx(skb);
+	__be16 tag16[RTL8_4_TAG_LEN / 2];
 
 	/* Set Realtek EtherType */
-	tag[0] = htons(ETH_P_REALTEK);
+	tag16[0] = htons(ETH_P_REALTEK);
 
 	/* Set Protocol; zero REASON */
-	tag[1] = htons(FIELD_PREP(RTL8_4_PROTOCOL, RTL8_4_PROTOCOL_RTL8365MB));
+	tag16[1] = htons(FIELD_PREP(RTL8_4_PROTOCOL, RTL8_4_PROTOCOL_RTL8365MB));
 
 	/* Zero FID_EN, FID, PRI_EN, PRI, KEEP; set LEARN_DIS */
-	tag[2] = htons(FIELD_PREP(RTL8_4_LEARN_DIS, 1));
+	tag16[2] = htons(FIELD_PREP(RTL8_4_LEARN_DIS, 1));
 
 	/* Zero ALLOW; set RX (CPU->switch) forwarding port mask */
-	tag[3] = htons(FIELD_PREP(RTL8_4_RX, BIT(dp->index)));
+	tag16[3] = htons(FIELD_PREP(RTL8_4_RX, BIT(dp->index)));
+
+	memcpy(tag, tag16, RTL8_4_TAG_LEN);
+}
+
+static struct sk_buff *rtl8_4_tag_xmit(struct sk_buff *skb,
+				       struct net_device *dev)
+{
+	skb_push(skb, RTL8_4_TAG_LEN);
+
+	dsa_alloc_etype_header(skb, RTL8_4_TAG_LEN);
+
+	rtl8_4_write_tag(skb, dev, dsa_etype_header_pos_tx(skb));
 
 	return skb;
 }
 
-static struct sk_buff *rtl8_4_tag_rcv(struct sk_buff *skb,
-				      struct net_device *dev)
+static struct sk_buff *rtl8_4t_tag_xmit(struct sk_buff *skb,
+					struct net_device *dev)
+{
+	/* Calculate the checksum here if not done yet as trailing tags will
+	 * break either software or hardware based checksum
+	 */
+	if (skb->ip_summed == CHECKSUM_PARTIAL && skb_checksum_help(skb))
+		return NULL;
+
+	rtl8_4_write_tag(skb, dev, skb_put(skb, RTL8_4_TAG_LEN));
+
+	return skb;
+}
+
+static int rtl8_4_read_tag(struct sk_buff *skb, struct net_device *dev,
+			   void *tag)
 {
-	__be16 *tag;
+	__be16 tag16[RTL8_4_TAG_LEN / 2];
 	u16 etype;
 	u8 reason;
 	u8 proto;
 	u8 port;
 
-	if (unlikely(!pskb_may_pull(skb, RTL8_4_TAG_LEN)))
-		return NULL;
-
-	tag = dsa_etype_header_pos_rx(skb);
+	memcpy(tag16, tag, RTL8_4_TAG_LEN);
 
 	/* Parse Realtek EtherType */
-	etype = ntohs(tag[0]);
+	etype = ntohs(tag16[0]);
 	if (unlikely(etype != ETH_P_REALTEK)) {
 		dev_warn_ratelimited(&dev->dev,
 				     "non-realtek ethertype 0x%04x\n", etype);
-		return NULL;
+		return -EPROTO;
 	}
 
 	/* Parse Protocol */
-	proto = FIELD_GET(RTL8_4_PROTOCOL, ntohs(tag[1]));
+	proto = FIELD_GET(RTL8_4_PROTOCOL, ntohs(tag16[1]));
 	if (unlikely(proto != RTL8_4_PROTOCOL_RTL8365MB)) {
 		dev_warn_ratelimited(&dev->dev,
 				     "unknown realtek protocol 0x%02x\n",
 				     proto);
-		return NULL;
+		return -EPROTO;
 	}
 
 	/* Parse REASON */
-	reason = FIELD_GET(RTL8_4_REASON, ntohs(tag[1]));
+	reason = FIELD_GET(RTL8_4_REASON, ntohs(tag16[1]));
 
 	/* Parse TX (switch->CPU) */
-	port = FIELD_GET(RTL8_4_TX, ntohs(tag[3]));
+	port = FIELD_GET(RTL8_4_TX, ntohs(tag16[3]));
 	skb->dev = dsa_master_find_slave(dev, 0, port);
 	if (!skb->dev) {
 		dev_warn_ratelimited(&dev->dev,
 				     "could not find slave for port %d\n",
 				     port);
-		return NULL;
+		return -ENOENT;
 	}
 
+	if (reason != RTL8_4_REASON_TRAP)
+		dsa_default_offload_fwd_mark(skb);
+
+	return 0;
+}
+
+static struct sk_buff *rtl8_4_tag_rcv(struct sk_buff *skb,
+				      struct net_device *dev)
+{
+	if (unlikely(!pskb_may_pull(skb, RTL8_4_TAG_LEN)))
+		return NULL;
+
+	if (unlikely(rtl8_4_read_tag(skb, dev, dsa_etype_header_pos_rx(skb))))
+		return NULL;
+
 	/* Remove tag and recalculate checksum */
 	skb_pull_rcsum(skb, RTL8_4_TAG_LEN);
 
 	dsa_strip_etype_header(skb, RTL8_4_TAG_LEN);
 
-	if (reason != RTL8_4_REASON_TRAP)
-		dsa_default_offload_fwd_mark(skb);
+	return skb;
+}
+
+static struct sk_buff *rtl8_4t_tag_rcv(struct sk_buff *skb,
+				       struct net_device *dev)
+{
+	if (skb_linearize(skb))
+		return NULL;
+
+	if (unlikely(rtl8_4_read_tag(skb, dev, skb_tail_pointer(skb) - RTL8_4_TAG_LEN)))
+		return NULL;
+
+	if (pskb_trim_rcsum(skb, skb->len - RTL8_4_TAG_LEN))
+		return NULL;
 
 	return skb;
 }
 
+/* Ethertype version */
 static const struct dsa_device_ops rtl8_4_netdev_ops = {
 	.name = "rtl8_4",
 	.proto = DSA_TAG_PROTO_RTL8_4,
@@ -172,7 +231,28 @@ static const struct dsa_device_ops rtl8_4_netdev_ops = {
 	.rcv = rtl8_4_tag_rcv,
 	.needed_headroom = RTL8_4_TAG_LEN,
 };
-module_dsa_tag_driver(rtl8_4_netdev_ops);
 
-MODULE_LICENSE("GPL");
+DSA_TAG_DRIVER(rtl8_4_netdev_ops);
+
 MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_RTL8_4);
+
+/* Tail version */
+static const struct dsa_device_ops rtl8_4t_netdev_ops = {
+	.name = "rtl8_4t",
+	.proto = DSA_TAG_PROTO_RTL8_4T,
+	.xmit = rtl8_4t_tag_xmit,
+	.rcv = rtl8_4t_tag_rcv,
+	.needed_tailroom = RTL8_4_TAG_LEN,
+};
+
+DSA_TAG_DRIVER(rtl8_4t_netdev_ops);
+
+MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_RTL8_4L);
+
+static struct dsa_tag_driver *dsa_tag_drivers[] = {
+	&DSA_TAG_DRIVER_NAME(rtl8_4_netdev_ops),
+	&DSA_TAG_DRIVER_NAME(rtl8_4t_netdev_ops),
+};
+module_dsa_tag_drivers(dsa_tag_drivers);
+
+MODULE_LICENSE("GPL");