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authorVladimir Oltean <olteanv@gmail.com>2019-06-08 15:04:42 +0300
committerDavid S. Miller <davem@davemloft.net>2019-06-08 15:20:40 -0700
commitf3097be21bf17ae8785eea009cbc424f16611d9a (patch)
treee21fd387d3a4914c2bf7b0322aaedb0d5172b23c /net/dsa
parent08fde09a0d1fd1391bdf828de3607c00193e6528 (diff)
net: dsa: sja1105: Add a state machine for RX timestamping
Meta frame reception relies on the hardware keeping its promise that it will send no other traffic towards the CPU port between a link-local frame and a meta frame. Otherwise there is no other way to associate the meta frame with the link-local frame it's holding a timestamp of. The receive function is made stateful, and buffers a timestampable frame until its meta frame arrives, then merges the two, drops the meta and releases the link-local frame up the stack. Signed-off-by: Vladimir Oltean <olteanv@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/dsa')
-rw-r--r--net/dsa/tag_sja1105.c121
1 files changed, 120 insertions, 1 deletions
diff --git a/net/dsa/tag_sja1105.c b/net/dsa/tag_sja1105.c
index 5b51e96130c7..1d96c9d4a8e9 100644
--- a/net/dsa/tag_sja1105.c
+++ b/net/dsa/tag_sja1105.c
@@ -110,6 +110,124 @@ static struct sk_buff *sja1105_xmit(struct sk_buff *skb,
((pcp << VLAN_PRIO_SHIFT) | tx_vid));
}
+static void sja1105_transfer_meta(struct sk_buff *skb,
+ const struct sja1105_meta *meta)
+{
+ struct ethhdr *hdr = eth_hdr(skb);
+
+ hdr->h_dest[3] = meta->dmac_byte_3;
+ hdr->h_dest[4] = meta->dmac_byte_4;
+ SJA1105_SKB_CB(skb)->meta_tstamp = meta->tstamp;
+}
+
+/* This is a simple state machine which follows the hardware mechanism of
+ * generating RX timestamps:
+ *
+ * After each timestampable skb (all traffic for which send_meta1 and
+ * send_meta0 is true, aka all MAC-filtered link-local traffic) a meta frame
+ * containing a partial timestamp is immediately generated by the switch and
+ * sent as a follow-up to the link-local frame on the CPU port.
+ *
+ * The meta frames have no unique identifier (such as sequence number) by which
+ * one may pair them to the correct timestampable frame.
+ * Instead, the switch has internal logic that ensures no frames are sent on
+ * the CPU port between a link-local timestampable frame and its corresponding
+ * meta follow-up. It also ensures strict ordering between ports (lower ports
+ * have higher priority towards the CPU port). For this reason, a per-port
+ * data structure is not needed/desirable.
+ *
+ * This function pairs the link-local frame with its partial timestamp from the
+ * meta follow-up frame. The full timestamp will be reconstructed later in a
+ * work queue.
+ */
+static struct sk_buff
+*sja1105_rcv_meta_state_machine(struct sk_buff *skb,
+ struct sja1105_meta *meta,
+ bool is_link_local,
+ bool is_meta)
+{
+ struct sja1105_port *sp;
+ struct dsa_port *dp;
+
+ dp = dsa_slave_to_port(skb->dev);
+ sp = dp->priv;
+
+ /* Step 1: A timestampable frame was received.
+ * Buffer it until we get its meta frame.
+ */
+ if (is_link_local && sp->data->hwts_rx_en) {
+ spin_lock(&sp->data->meta_lock);
+ /* Was this a link-local frame instead of the meta
+ * that we were expecting?
+ */
+ if (sp->data->stampable_skb) {
+ dev_err_ratelimited(dp->ds->dev,
+ "Expected meta frame, is %12llx "
+ "in the DSA master multicast filter?\n",
+ SJA1105_META_DMAC);
+ }
+
+ /* Hold a reference to avoid dsa_switch_rcv
+ * from freeing the skb.
+ */
+ sp->data->stampable_skb = skb_get(skb);
+ spin_unlock(&sp->data->meta_lock);
+
+ /* Tell DSA we got nothing */
+ return NULL;
+
+ /* Step 2: The meta frame arrived.
+ * Time to take the stampable skb out of the closet, annotate it
+ * with the partial timestamp, and pretend that we received it
+ * just now (basically masquerade the buffered frame as the meta
+ * frame, which serves no further purpose).
+ */
+ } else if (is_meta) {
+ struct sk_buff *stampable_skb;
+
+ spin_lock(&sp->data->meta_lock);
+
+ stampable_skb = sp->data->stampable_skb;
+ sp->data->stampable_skb = NULL;
+
+ /* Was this a meta frame instead of the link-local
+ * that we were expecting?
+ */
+ if (!stampable_skb) {
+ dev_err_ratelimited(dp->ds->dev,
+ "Unexpected meta frame\n");
+ spin_unlock(&sp->data->meta_lock);
+ return NULL;
+ }
+
+ if (stampable_skb->dev != skb->dev) {
+ dev_err_ratelimited(dp->ds->dev,
+ "Meta frame on wrong port\n");
+ spin_unlock(&sp->data->meta_lock);
+ return NULL;
+ }
+
+ /* Free the meta frame and give DSA the buffered stampable_skb
+ * for further processing up the network stack.
+ */
+ kfree_skb(skb);
+
+ skb = skb_copy(stampable_skb, GFP_ATOMIC);
+ if (!skb) {
+ dev_err_ratelimited(dp->ds->dev,
+ "Failed to copy stampable skb\n");
+ return NULL;
+ }
+ sja1105_transfer_meta(skb, meta);
+ /* The cached copy will be freed now */
+ skb_unref(stampable_skb);
+
+ spin_unlock(&sp->data->meta_lock);
+ }
+
+ return skb;
+}
+
static struct sk_buff *sja1105_rcv(struct sk_buff *skb,
struct net_device *netdev,
struct packet_type *pt)
@@ -167,7 +285,8 @@ static struct sk_buff *sja1105_rcv(struct sk_buff *skb,
if (is_tagged)
skb = dsa_8021q_remove_header(skb);
- return skb;
+ return sja1105_rcv_meta_state_machine(skb, &meta, is_link_local,
+ is_meta);
}
static struct dsa_device_ops sja1105_netdev_ops = {