linux-kernel - [PATCH v3 net-next 13/17] net: dsa: sja1105: Receive and decode meta frames

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Date:   Tue,  4 Jun 2019 20:07:52 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     f.fainelli@...il.com, vivien.didelot@...il.com, andrew@...n.ch,
        davem@...emloft.net, richardcochran@...il.com,
        john.stultz@...aro.org, tglx@...utronix.de, sboyd@...nel.org
Cc:     linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        Vladimir Oltean <olteanv@...il.com>
Subject: [PATCH v3 net-next 13/17] net: dsa: sja1105: Receive and decode meta frames

This adds support in the tagger for understanding the source port and
switch id of meta frames.  Their timestamp is also extracted but not
used yet - this needs to be done in a state machine that modifies the
previously received timestampable frame - will be added in a follow-up
patch.

Signed-off-by: Vladimir Oltean <olteanv@...il.com>
---
Changes in v3:

Split from previous 09/10 patch (no functional changes).

Changes in v2:

None.

 net/dsa/tag_sja1105.c | 43 ++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 42 insertions(+), 1 deletion(-)

diff --git a/net/dsa/tag_sja1105.c b/net/dsa/tag_sja1105.c
index 9ff7cfa6ea20..6ec9a32dda62 100644
--- a/net/dsa/tag_sja1105.c
+++ b/net/dsa/tag_sja1105.c
@@ -7,6 +7,36 @@
 #include <linux/packing.h>
 #include "dsa_priv.h"
 
+struct sja1105_meta {
+	u64 tstamp;
+	u64 dmac_byte_4;
+	u64 dmac_byte_3;
+	u64 source_port;
+	u64 switch_id;
+};
+
+static void sja1105_meta_unpack(const struct sk_buff *skb,
+				struct sja1105_meta *meta)
+{
+	u8 *buf = skb_mac_header(skb) + ETH_HLEN;
+
+	/* UM10944.pdf section 4.2.17 AVB Parameters:
+	 * Structure of the meta-data follow-up frame.
+	 * It is in network byte order, so there are no quirks
+	 * while unpacking the meta frame.
+	 *
+	 * Also SJA1105 E/T only populates bits 23:0 of the timestamp
+	 * whereas P/Q/R/S does 32 bits. Since the structure is the
+	 * same and the E/T puts zeroes in the high-order byte, use
+	 * a unified unpacking command for both device series.
+	 */
+	packing(buf,     &meta->tstamp,     31, 0, 4, UNPACK, 0);
+	packing(buf + 4, &meta->dmac_byte_4, 7, 0, 1, UNPACK, 0);
+	packing(buf + 5, &meta->dmac_byte_3, 7, 0, 1, UNPACK, 0);
+	packing(buf + 6, &meta->source_port, 7, 0, 1, UNPACK, 0);
+	packing(buf + 7, &meta->switch_id,   7, 0, 1, UNPACK, 0);
+}
+
 static inline bool sja1105_is_meta_frame(const struct sk_buff *skb)
 {
 	const struct ethhdr *hdr = eth_hdr(skb);
@@ -28,6 +58,8 @@ static inline bool sja1105_is_meta_frame(const struct sk_buff *skb)
  */
 static bool sja1105_filter(const struct sk_buff *skb, struct net_device *dev)
 {
+	if (sja1105_is_meta_frame(skb))
+		return true;
 	if (sja1105_is_link_local(skb))
 		return true;
 	if (!dsa_port_is_vlan_filtering(dev->dsa_ptr))
@@ -66,13 +98,18 @@ static struct sk_buff *sja1105_rcv(struct sk_buff *skb,
 				   struct net_device *netdev,
 				   struct packet_type *pt)
 {
+	struct sja1105_meta meta = {0};
 	int source_port, switch_id;
 	struct sk_buff *nskb;
 	u16 tpid, vid, tci;
+	bool is_link_local;
 	bool is_tagged;
+	bool is_meta;
 
 	nskb = dsa_8021q_rcv(skb, netdev, pt, &tpid, &tci);
 	is_tagged = (nskb && tpid == ETH_P_SJA1105);
+	is_link_local = sja1105_is_link_local(skb);
+	is_meta = sja1105_is_meta_frame(skb);
 
 	skb->offload_fwd_mark = 1;
 
@@ -82,7 +119,7 @@ static struct sk_buff *sja1105_rcv(struct sk_buff *skb,
 		source_port = dsa_8021q_rx_source_port(vid);
 		switch_id = dsa_8021q_rx_switch_id(vid);
 		skb->priority = (tci & VLAN_PRIO_MASK) >> VLAN_PRIO_SHIFT;
-	} else if (sja1105_is_link_local(skb)) {
+	} else if (is_link_local) {
 		struct ethhdr *hdr = eth_hdr(skb);
 
 		/* Management traffic path. Switch embeds the switch ID and
@@ -94,6 +131,10 @@ static struct sk_buff *sja1105_rcv(struct sk_buff *skb,
 		/* Clear the DMAC bytes that were mangled by the switch */
 		hdr->h_dest[3] = 0;
 		hdr->h_dest[4] = 0;
+	} else if (is_meta) {
+		sja1105_meta_unpack(skb, &meta);
+		source_port = meta.source_port;
+		switch_id = meta.switch_id;
 	} else {
 		return NULL;
 	}
-- 
2.17.1