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>
This commit is contained in:
Vladimir Oltean 2019-06-08 15:04:42 +03:00 committed by David S. Miller
parent 08fde09a0d
commit f3097be21b
3 changed files with 189 additions and 1 deletions

View File

@ -1600,6 +1600,14 @@ static int sja1105_setup(struct dsa_switch *ds)
return sja1105_setup_8021q_tagging(ds, true);
}
static void sja1105_teardown(struct dsa_switch *ds)
{
struct sja1105_private *priv = ds->priv;
cancel_work_sync(&priv->tagger_data.rxtstamp_work);
skb_queue_purge(&priv->tagger_data.skb_rxtstamp_queue);
}
static int sja1105_mgmt_xmit(struct dsa_switch *ds, int port, int slot,
struct sk_buff *skb, bool takets)
{
@ -1747,6 +1755,57 @@ static int sja1105_set_ageing_time(struct dsa_switch *ds,
return sja1105_static_config_reload(priv);
}
#define to_tagger(d) \
container_of((d), struct sja1105_tagger_data, rxtstamp_work)
#define to_sja1105(d) \
container_of((d), struct sja1105_private, tagger_data)
static void sja1105_rxtstamp_work(struct work_struct *work)
{
struct sja1105_tagger_data *data = to_tagger(work);
struct sja1105_private *priv = to_sja1105(data);
struct sk_buff *skb;
u64 now;
mutex_lock(&priv->ptp_lock);
now = priv->tstamp_cc.read(&priv->tstamp_cc);
while ((skb = skb_dequeue(&data->skb_rxtstamp_queue)) != NULL) {
struct skb_shared_hwtstamps *shwt = skb_hwtstamps(skb);
u64 ts;
*shwt = (struct skb_shared_hwtstamps) {0};
ts = SJA1105_SKB_CB(skb)->meta_tstamp;
ts = sja1105_tstamp_reconstruct(priv, now, ts);
ts = timecounter_cyc2time(&priv->tstamp_tc, ts);
shwt->hwtstamp = ns_to_ktime(ts);
netif_rx_ni(skb);
}
mutex_unlock(&priv->ptp_lock);
}
/* Called from dsa_skb_defer_rx_timestamp */
bool sja1105_port_rxtstamp(struct dsa_switch *ds, int port,
struct sk_buff *skb, unsigned int type)
{
struct sja1105_private *priv = ds->priv;
struct sja1105_tagger_data *data = &priv->tagger_data;
if (!data->hwts_rx_en)
return false;
/* We need to read the full PTP clock to reconstruct the Rx
* timestamp. For that we need a sleepable context.
*/
skb_queue_tail(&data->skb_rxtstamp_queue, skb);
schedule_work(&data->rxtstamp_work);
return true;
}
/* Called from dsa_skb_tx_timestamp. This callback is just to make DSA clone
* the skb and have it available in DSA_SKB_CB in the .port_deferred_xmit
* callback, where we will timestamp it synchronously.
@ -1766,6 +1825,7 @@ bool sja1105_port_txtstamp(struct dsa_switch *ds, int port,
static const struct dsa_switch_ops sja1105_switch_ops = {
.get_tag_protocol = sja1105_get_tag_protocol,
.setup = sja1105_setup,
.teardown = sja1105_teardown,
.set_ageing_time = sja1105_set_ageing_time,
.phylink_validate = sja1105_phylink_validate,
.phylink_mac_config = sja1105_mac_config,
@ -1787,6 +1847,7 @@ static const struct dsa_switch_ops sja1105_switch_ops = {
.port_mdb_add = sja1105_mdb_add,
.port_mdb_del = sja1105_mdb_del,
.port_deferred_xmit = sja1105_port_deferred_xmit,
.port_rxtstamp = sja1105_port_rxtstamp,
.port_txtstamp = sja1105_port_txtstamp,
};
@ -1885,6 +1946,7 @@ static int sja1105_probe(struct spi_device *spi)
tagger_data = &priv->tagger_data;
skb_queue_head_init(&tagger_data->skb_rxtstamp_queue);
INIT_WORK(&tagger_data->rxtstamp_work, sja1105_rxtstamp_work);
/* Connections between dsa_port and sja1105_port */
for (i = 0; i < SJA1105_NUM_PORTS; i++) {

View File

@ -45,6 +45,13 @@ struct sja1105_tagger_data {
bool hwts_rx_en;
};
struct sja1105_skb_cb {
u32 meta_tstamp;
};
#define SJA1105_SKB_CB(skb) \
((struct sja1105_skb_cb *)DSA_SKB_CB_PRIV(skb))
struct sja1105_port {
struct sja1105_tagger_data *data;
struct dsa_port *dp;

View File

@ -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 = {