net: dsa: add support for the SJA1110 native tagging protocol

The SJA1110 has improved a few things compared to SJA1105:

- To send a control packet from the host port with SJA1105, one needed
  to program a one-shot "management route" over SPI. This is no longer
  true with SJA1110, you can actually send "in-band control extensions"
  in the packets sent by DSA, these are in fact DSA tags which contain
  the destination port and switch ID.

- When receiving a control packet from the switch with SJA1105, the
  source port and switch ID were written in bytes 3 and 4 of the
  destination MAC address of the frame (which was a very poor shot at a
  DSA header). If the control packet also had an RX timestamp, that
  timestamp was sent in an actual follow-up packet, so there were
  reordering concerns on multi-core/multi-queue DSA masters, where the
  metadata frame with the RX timestamp might get processed before the
  actual packet to which that timestamp belonged (there is no way to
  pair a packet to its timestamp other than the order in which they were
  received). On SJA1110, this is no longer true, control packets have
  the source port, switch ID and timestamp all in the DSA tags.

- Timestamps from the switch were partial: to get a 64-bit timestamp as
  required by PTP stacks, one would need to take the partial 24-bit or
  32-bit timestamp from the packet, then read the current PTP time very
  quickly, and then patch in the high bits of the current PTP time into
  the captured partial timestamp, to reconstruct what the full 64-bit
  timestamp must have been. That is awful because packet processing is
  done in NAPI context, but reading the current PTP time is done over
  SPI and therefore needs sleepable context.

But it also aggravated a few things:

- Not only is there a DSA header in SJA1110, but there is a DSA trailer
  in fact, too. So DSA needs to be extended to support taggers which
  have both a header and a trailer. Very unconventional - my understanding
  is that the trailer exists because the timestamps couldn't be prepared
  in time for putting them in the header area.

- Like SJA1105, not all packets sent to the CPU have the DSA tag added
  to them, only control packets do:

  * the ones which match the destination MAC filters/traps in
    MAC_FLTRES1 and MAC_FLTRES0
  * the ones which match FDB entries which have TRAP or TAKETS bits set

  So we could in theory hack something up to request the switch to take
  timestamps for all packets that reach the CPU, and those would be
  DSA-tagged and contain the source port / switch ID by virtue of the
  fact that there needs to be a timestamp trailer provided. BUT:

- The SJA1110 does not parse its own DSA tags in a way that is useful
  for routing in cross-chip topologies, a la Marvell. And the sja1105
  driver already supports cross-chip bridging from the SJA1105 days.
  It does that by automatically setting up the DSA links as VLAN trunks
  which contain all the necessary tag_8021q RX VLANs that must be
  communicated between the switches that span the same bridge. So when
  using tag_8021q on sja1105, it is possible to have 2 switches with
  ports sw0p0, sw0p1, sw1p0, sw1p1, and 2 VLAN-unaware bridges br0 and
  br1, and br0 can take sw0p0 and sw1p0, and br1 can take sw0p1 and
  sw1p1, and forwarding will happen according to the expected rules of
  the Linux bridge.
  We like that, and we don't want that to go away, so as a matter of
  fact, the SJA1110 tagger still needs to support tag_8021q.

So the sja1110 tagger is a hybrid between tag_8021q for data packets,
and the native hardware support for control packets.

On RX, packets have a 13-byte trailer if they contain an RX timestamp.
That trailer is padded in such a way that its byte 8 (the start of the
"residence time" field - not parsed by Linux because we don't care) is
aligned on a 16 byte boundary. So the padding has a variable length
between 0 and 15 bytes. The DSA header contains the offset of the
beginning of the padding relative to the beginning of the frame (and the
end of the padding is obviously the end of the packet minus 13 bytes,
the length of the trailer). So we discard it.

Packets which don't have a trailer contain the source port and switch ID
information in the header (they are "trap-to-host" packets). Packets
which have a trailer contain the source port and switch ID in the trailer.

On TX, the destination port mask and switch ID is always in the trailer,
so we always need to say in the header that a trailer is present.

The header needs a custom EtherType and this was chosen as 0xdadc, after
0xdada which is for Marvell and 0xdadb which is for VLANs in
VLAN-unaware mode on SJA1105 (and SJA1110 in fact too).

Because we use tag_8021q in concert with the native tagging protocol,
control packets will have 2 DSA tags.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 219 insertions, 2 deletions

diff --git a/net/dsa/tag_sja1105.c b/net/dsa/tag_sja1105.c
index 11f555dd9566..37e1d64e07c6 100644
--- a/net/dsa/tag_sja1105.c
+++ b/net/dsa/tag_sja1105.c
@@ -7,6 +7,47 @@
 #include <linux/packing.h>
 #include "dsa_priv.h"
 
+/* Is this a TX or an RX header? */
+#define SJA1110_HEADER_HOST_TO_SWITCH		BIT(15)
+
+/* RX header */
+#define SJA1110_RX_HEADER_IS_METADATA		BIT(14)
+#define SJA1110_RX_HEADER_HOST_ONLY		BIT(13)
+#define SJA1110_RX_HEADER_HAS_TRAILER		BIT(12)
+
+/* Trap-to-host format (no trailer present) */
+#define SJA1110_RX_HEADER_SRC_PORT(x)		(((x) & GENMASK(7, 4)) >> 4)
+#define SJA1110_RX_HEADER_SWITCH_ID(x)		((x) & GENMASK(3, 0))
+
+/* Timestamp format (trailer present) */
+#define SJA1110_RX_HEADER_TRAILER_POS(x)	((x) & GENMASK(11, 0))
+
+#define SJA1110_RX_TRAILER_SWITCH_ID(x)		(((x) & GENMASK(7, 4)) >> 4)
+#define SJA1110_RX_TRAILER_SRC_PORT(x)		((x) & GENMASK(3, 0))
+
+/* TX header */
+#define SJA1110_TX_HEADER_UPDATE_TC		BIT(14)
+#define SJA1110_TX_HEADER_TAKE_TS		BIT(13)
+#define SJA1110_TX_HEADER_TAKE_TS_CASC		BIT(12)
+#define SJA1110_TX_HEADER_HAS_TRAILER		BIT(11)
+
+/* Only valid if SJA1110_TX_HEADER_HAS_TRAILER is false */
+#define SJA1110_TX_HEADER_PRIO(x)		(((x) << 7) & GENMASK(10, 7))
+#define SJA1110_TX_HEADER_TSTAMP_ID(x)		((x) & GENMASK(7, 0))
+
+/* Only valid if SJA1110_TX_HEADER_HAS_TRAILER is true */
+#define SJA1110_TX_HEADER_TRAILER_POS(x)	((x) & GENMASK(10, 0))
+
+#define SJA1110_TX_TRAILER_TSTAMP_ID(x)		(((x) << 24) & GENMASK(31, 24))
+#define SJA1110_TX_TRAILER_PRIO(x)		(((x) << 21) & GENMASK(23, 21))
+#define SJA1110_TX_TRAILER_SWITCHID(x)		(((x) << 12) & GENMASK(15, 12))
+#define SJA1110_TX_TRAILER_DESTPORTS(x)		(((x) << 1) & GENMASK(11, 1))
+
+#define SJA1110_HEADER_LEN			4
+#define SJA1110_RX_TRAILER_LEN			13
+#define SJA1110_TX_TRAILER_LEN			4
+#define SJA1110_MAX_PADDING_LEN			15
+
 /* Similar to is_link_local_ether_addr(hdr->h_dest) but also covers PTP */
 static inline bool sja1105_is_link_local(const struct sk_buff *skb)
 {
@@ -140,6 +181,50 @@ static struct sk_buff *sja1105_xmit(struct sk_buff *skb,
 			     ((pcp << VLAN_PRIO_SHIFT) | tx_vid));
 }
 
+static struct sk_buff *sja1110_xmit(struct sk_buff *skb,
+				    struct net_device *netdev)
+{
+	struct dsa_port *dp = dsa_slave_to_port(netdev);
+	u16 tx_vid = dsa_8021q_tx_vid(dp->ds, dp->index);
+	u16 queue_mapping = skb_get_queue_mapping(skb);
+	u8 pcp = netdev_txq_to_tc(netdev, queue_mapping);
+	struct ethhdr *eth_hdr;
+	__be32 *tx_trailer;
+	__be16 *tx_header;
+	int trailer_pos;
+
+	/* Transmitting control packets is done using in-band control
+	 * extensions, while data packets are transmitted using
+	 * tag_8021q TX VLANs.
+	 */
+	if (likely(!sja1105_is_link_local(skb)))
+		return dsa_8021q_xmit(skb, netdev, sja1105_xmit_tpid(dp->priv),
+				     ((pcp << VLAN_PRIO_SHIFT) | tx_vid));
+
+	skb_push(skb, SJA1110_HEADER_LEN);
+
+	/* Move Ethernet header to the left, making space for DSA tag */
+	memmove(skb->data, skb->data + SJA1110_HEADER_LEN, 2 * ETH_ALEN);
+
+	trailer_pos = skb->len;
+
+	/* On TX, skb->data points to skb_mac_header(skb) */
+	eth_hdr = (struct ethhdr *)skb->data;
+	tx_header = (__be16 *)(eth_hdr + 1);
+	tx_trailer = skb_put(skb, SJA1110_TX_TRAILER_LEN);
+
+	eth_hdr->h_proto = htons(ETH_P_SJA1110);
+
+	*tx_header = htons(SJA1110_HEADER_HOST_TO_SWITCH |
+			   SJA1110_TX_HEADER_HAS_TRAILER |
+			   SJA1110_TX_HEADER_TRAILER_POS(trailer_pos));
+	*tx_trailer = cpu_to_be32(SJA1110_TX_TRAILER_PRIO(pcp) |
+				  SJA1110_TX_TRAILER_SWITCHID(dp->ds->index) |
+				  SJA1110_TX_TRAILER_DESTPORTS(BIT(dp->index)));
+
+	return skb;
+}
+
 static void sja1105_transfer_meta(struct sk_buff *skb,
 				  const struct sja1105_meta *meta)
 {
@@ -283,6 +368,11 @@ static bool sja1105_skb_has_tag_8021q(const struct sk_buff *skb)
 	       skb_vlan_tag_present(skb);
 }
 
+static bool sja1110_skb_has_inband_control_extension(const struct sk_buff *skb)
+{
+	return ntohs(eth_hdr(skb)->h_proto) == ETH_P_SJA1110;
+}
+
 static struct sk_buff *sja1105_rcv(struct sk_buff *skb,
 				   struct net_device *netdev,
 				   struct packet_type *pt)
@@ -333,6 +423,98 @@ static struct sk_buff *sja1105_rcv(struct sk_buff *skb,
 					      is_meta);
 }
 
+static struct sk_buff *sja1110_rcv_inband_control_extension(struct sk_buff *skb,
+							    int *source_port,
+							    int *switch_id)
+{
+	u16 rx_header;
+
+	if (unlikely(!pskb_may_pull(skb, SJA1110_HEADER_LEN)))
+		return NULL;
+
+	/* skb->data points to skb_mac_header(skb) + ETH_HLEN, which is exactly
+	 * what we need because the caller has checked the EtherType (which is
+	 * located 2 bytes back) and we just need a pointer to the header that
+	 * comes afterwards.
+	 */
+	rx_header = ntohs(*(__be16 *)skb->data);
+
+	/* Timestamp frame, we have a trailer */
+	if (rx_header & SJA1110_RX_HEADER_HAS_TRAILER) {
+		int start_of_padding = SJA1110_RX_HEADER_TRAILER_POS(rx_header);
+		u8 *rx_trailer = skb_tail_pointer(skb) - SJA1110_RX_TRAILER_LEN;
+		u64 *tstamp = &SJA1105_SKB_CB(skb)->tstamp;
+		u8 last_byte = rx_trailer[12];
+
+		/* The timestamp is unaligned, so we need to use packing()
+		 * to get it
+		 */
+		packing(rx_trailer, tstamp, 63, 0, 8, UNPACK, 0);
+
+		*source_port = SJA1110_RX_TRAILER_SRC_PORT(last_byte);
+		*switch_id = SJA1110_RX_TRAILER_SWITCH_ID(last_byte);
+
+		/* skb->len counts from skb->data, while start_of_padding
+		 * counts from the destination MAC address. Right now skb->data
+		 * is still as set by the DSA master, so to trim away the
+		 * padding and trailer we need to account for the fact that
+		 * skb->data points to skb_mac_header(skb) + ETH_HLEN.
+		 */
+		pskb_trim_rcsum(skb, start_of_padding - ETH_HLEN);
+	/* Trap-to-host frame, no timestamp trailer */
+	} else {
+		*source_port = SJA1110_RX_HEADER_SRC_PORT(rx_header);
+		*switch_id = SJA1110_RX_HEADER_SWITCH_ID(rx_header);
+	}
+
+	/* Advance skb->data past the DSA header */
+	skb_pull_rcsum(skb, SJA1110_HEADER_LEN);
+
+	/* Remove the DSA header */
+	memmove(skb->data - ETH_HLEN, skb->data - ETH_HLEN - SJA1110_HEADER_LEN,
+		2 * ETH_ALEN);
+
+	/* With skb->data in its final place, update the MAC header
+	 * so that eth_hdr() continues to works properly.
+	 */
+	skb_set_mac_header(skb, -ETH_HLEN);
+
+	return skb;
+}
+
+static struct sk_buff *sja1110_rcv(struct sk_buff *skb,
+				   struct net_device *netdev,
+				   struct packet_type *pt)
+{
+	int source_port = -1, switch_id = -1, subvlan = 0;
+
+	skb->offload_fwd_mark = 1;
+
+	if (sja1110_skb_has_inband_control_extension(skb)) {
+		skb = sja1110_rcv_inband_control_extension(skb, &source_port,
+							   &switch_id);
+		if (!skb)
+			return NULL;
+	}
+
+	/* Packets with in-band control extensions might still have RX VLANs */
+	if (likely(sja1105_skb_has_tag_8021q(skb)))
+		dsa_8021q_rcv(skb, &source_port, &switch_id, &subvlan);
+
+	skb->dev = dsa_master_find_slave(netdev, switch_id, source_port);
+	if (!skb->dev) {
+		netdev_warn(netdev,
+			    "Couldn't decode source port %d and switch id %d\n",
+			    source_port, switch_id);
+		return NULL;
+	}
+
+	if (subvlan)
+		sja1105_decode_subvlan(skb, subvlan);
+
+	return skb;
+}
+
 static void sja1105_flow_dissect(const struct sk_buff *skb, __be16 *proto,
 				 int *offset)
 {
@@ -343,6 +525,20 @@ static void sja1105_flow_dissect(const struct sk_buff *skb, __be16 *proto,
 	dsa_tag_generic_flow_dissect(skb, proto, offset);
 }
 
+static void sja1110_flow_dissect(const struct sk_buff *skb, __be16 *proto,
+				 int *offset)
+{
+	/* Management frames have 2 DSA tags on RX, so the needed_headroom we
+	 * declared is fine for the generic dissector adjustment procedure.
+	 */
+	if (unlikely(sja1105_is_link_local(skb)))
+		return dsa_tag_generic_flow_dissect(skb, proto, offset);
+
+	/* For the rest, there is a single DSA tag, the tag_8021q one */
+	*offset = VLAN_HLEN;
+	*proto = ((__be16 *)skb->data)[(VLAN_HLEN / 2) - 1];
+}
+
 static const struct dsa_device_ops sja1105_netdev_ops = {
 	.name = "sja1105",
 	.proto = DSA_TAG_PROTO_SJA1105,
@@ -354,7 +550,28 @@ static const struct dsa_device_ops sja1105_netdev_ops = {
 	.promisc_on_master = true,
 };
 
-MODULE_LICENSE("GPL v2");
+DSA_TAG_DRIVER(sja1105_netdev_ops);
 MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_SJA1105);
 
-module_dsa_tag_driver(sja1105_netdev_ops);
+static const struct dsa_device_ops sja1110_netdev_ops = {
+	.name = "sja1110",
+	.proto = DSA_TAG_PROTO_SJA1110,
+	.xmit = sja1110_xmit,
+	.rcv = sja1110_rcv,
+	.filter = sja1105_filter,
+	.flow_dissect = sja1110_flow_dissect,
+	.needed_headroom = SJA1110_HEADER_LEN + VLAN_HLEN,
+	.needed_tailroom = SJA1110_RX_TRAILER_LEN + SJA1110_MAX_PADDING_LEN,
+};
+
+DSA_TAG_DRIVER(sja1110_netdev_ops);
+MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_SJA1110);
+
+static struct dsa_tag_driver *sja1105_tag_driver_array[] = {
+	&DSA_TAG_DRIVER_NAME(sja1105_netdev_ops),
+	&DSA_TAG_DRIVER_NAME(sja1110_netdev_ops),
+};
+
+module_dsa_tag_drivers(sja1105_tag_driver_array);
+
+MODULE_LICENSE("GPL v2");