6.6-stable review patch. If anyone has any objections, please let me know.
------------------
From: Vladimir Oltean vladimir.oltean@nxp.com
[ Upstream commit b454abfab52543c44b581afc807b9f97fc1e7a3a ]
The Felix DSA driver presents unique challenges that make the simplistic ocelot PTP TX timestamping procedure unreliable: any transmitted packet may be lost in hardware before it ever leaves our local system.
This may happen because there is congestion on the DSA conduit, the switch CPU port or even user port (Qdiscs like taprio may delay packets indefinitely by design).
The technical problem is that the kernel, i.e. ocelot_port_add_txtstamp_skb(), runs out of timestamp IDs eventually, because it never detects that packets are lost, and keeps the IDs of the lost packets on hold indefinitely. The manifestation of the issue once the entire timestamp ID range becomes busy looks like this in dmesg:
mscc_felix 0000:00:00.5: port 0 delivering skb without TX timestamp mscc_felix 0000:00:00.5: port 1 delivering skb without TX timestamp
At the surface level, we need a timeout timer so that the kernel knows a timestamp ID is available again. But there is a deeper problem with the implementation, which is the monotonically increasing ocelot_port->ts_id. In the presence of packet loss, it will be impossible to detect that and reuse one of the holes created in the range of free timestamp IDs.
What we actually need is a bitmap of 63 timestamp IDs tracking which one is available. That is able to use up holes caused by packet loss, but also gives us a unique opportunity to not implement an actual timer_list for the timeout timer (very complicated in terms of locking).
We could only declare a timestamp ID stale on demand (lazily), aka when there's no other timestamp ID available. There are pros and cons to this approach: the implementation is much more simple than per-packet timers would be, but most of the stale packets would be quasi-leaked - not really leaked, but blocked in driver memory, since this algorithm sees no reason to free them.
An improved technique would be to check for stale timestamp IDs every time we allocate a new one. Assuming a constant flux of PTP packets, this avoids stale packets being blocked in memory, but of course, packets lost at the end of the flux are still blocked until the flux resumes (nobody left to kick them out).
Since implementing per-packet timers is way too complicated, this should be good enough.
Testing procedure:
Persistently block traffic class 5 and try to run PTP on it: $ tc qdisc replace dev swp3 parent root taprio num_tc 8 \ map 0 1 2 3 4 5 6 7 queues 1@0 1@1 1@2 1@3 1@4 1@5 1@6 1@7 \ base-time 0 sched-entry S 0xdf 100000 flags 0x2 [ 126.948141] mscc_felix 0000:00:00.5: port 3 tc 5 min gate length 0 ns not enough for max frame size 1526 at 1000 Mbps, dropping frames over 1 octets including FCS $ ptp4l -i swp3 -2 -P -m --socket_priority 5 --fault_reset_interval ASAP --logSyncInterval -3 ptp4l[70.351]: port 1 (swp3): INITIALIZING to LISTENING on INIT_COMPLETE ptp4l[70.354]: port 0 (/var/run/ptp4l): INITIALIZING to LISTENING on INIT_COMPLETE ptp4l[70.358]: port 0 (/var/run/ptp4lro): INITIALIZING to LISTENING on INIT_COMPLETE [ 70.394583] mscc_felix 0000:00:00.5: port 3 timestamp id 0 ptp4l[70.406]: timed out while polling for tx timestamp ptp4l[70.406]: increasing tx_timestamp_timeout or increasing kworker priority may correct this issue, but a driver bug likely causes it ptp4l[70.406]: port 1 (swp3): send peer delay response failed ptp4l[70.407]: port 1 (swp3): clearing fault immediately ptp4l[70.952]: port 1 (swp3): new foreign master d858d7.fffe.00ca6d-1 [ 71.394858] mscc_felix 0000:00:00.5: port 3 timestamp id 1 ptp4l[71.400]: timed out while polling for tx timestamp ptp4l[71.400]: increasing tx_timestamp_timeout or increasing kworker priority may correct this issue, but a driver bug likely causes it ptp4l[71.401]: port 1 (swp3): send peer delay response failed ptp4l[71.401]: port 1 (swp3): clearing fault immediately [ 72.393616] mscc_felix 0000:00:00.5: port 3 timestamp id 2 ptp4l[72.401]: timed out while polling for tx timestamp ptp4l[72.402]: increasing tx_timestamp_timeout or increasing kworker priority may correct this issue, but a driver bug likely causes it ptp4l[72.402]: port 1 (swp3): send peer delay response failed ptp4l[72.402]: port 1 (swp3): clearing fault immediately ptp4l[72.952]: port 1 (swp3): new foreign master d858d7.fffe.00ca6d-1 [ 73.395291] mscc_felix 0000:00:00.5: port 3 timestamp id 3 ptp4l[73.400]: timed out while polling for tx timestamp ptp4l[73.400]: increasing tx_timestamp_timeout or increasing kworker priority may correct this issue, but a driver bug likely causes it ptp4l[73.400]: port 1 (swp3): send peer delay response failed ptp4l[73.400]: port 1 (swp3): clearing fault immediately [ 74.394282] mscc_felix 0000:00:00.5: port 3 timestamp id 4 ptp4l[74.400]: timed out while polling for tx timestamp ptp4l[74.401]: increasing tx_timestamp_timeout or increasing kworker priority may correct this issue, but a driver bug likely causes it ptp4l[74.401]: port 1 (swp3): send peer delay response failed ptp4l[74.401]: port 1 (swp3): clearing fault immediately ptp4l[74.953]: port 1 (swp3): new foreign master d858d7.fffe.00ca6d-1 [ 75.396830] mscc_felix 0000:00:00.5: port 3 invalidating stale timestamp ID 0 which seems lost [ 75.405760] mscc_felix 0000:00:00.5: port 3 timestamp id 0 ptp4l[75.410]: timed out while polling for tx timestamp ptp4l[75.411]: increasing tx_timestamp_timeout or increasing kworker priority may correct this issue, but a driver bug likely causes it ptp4l[75.411]: port 1 (swp3): send peer delay response failed ptp4l[75.411]: port 1 (swp3): clearing fault immediately (...)
Remove the blocking condition and see that the port recovers: $ same tc command as above, but use "sched-entry S 0xff" instead $ same ptp4l command as above ptp4l[99.489]: port 1 (swp3): INITIALIZING to LISTENING on INIT_COMPLETE ptp4l[99.490]: port 0 (/var/run/ptp4l): INITIALIZING to LISTENING on INIT_COMPLETE ptp4l[99.492]: port 0 (/var/run/ptp4lro): INITIALIZING to LISTENING on INIT_COMPLETE [ 100.403768] mscc_felix 0000:00:00.5: port 3 invalidating stale timestamp ID 0 which seems lost [ 100.412545] mscc_felix 0000:00:00.5: port 3 invalidating stale timestamp ID 1 which seems lost [ 100.421283] mscc_felix 0000:00:00.5: port 3 invalidating stale timestamp ID 2 which seems lost [ 100.430015] mscc_felix 0000:00:00.5: port 3 invalidating stale timestamp ID 3 which seems lost [ 100.438744] mscc_felix 0000:00:00.5: port 3 invalidating stale timestamp ID 4 which seems lost [ 100.447470] mscc_felix 0000:00:00.5: port 3 timestamp id 0 [ 100.505919] mscc_felix 0000:00:00.5: port 3 timestamp id 0 ptp4l[100.963]: port 1 (swp3): new foreign master d858d7.fffe.00ca6d-1 [ 101.405077] mscc_felix 0000:00:00.5: port 3 timestamp id 0 [ 101.507953] mscc_felix 0000:00:00.5: port 3 timestamp id 0 [ 102.405405] mscc_felix 0000:00:00.5: port 3 timestamp id 0 [ 102.509391] mscc_felix 0000:00:00.5: port 3 timestamp id 0 [ 103.406003] mscc_felix 0000:00:00.5: port 3 timestamp id 0 [ 103.510011] mscc_felix 0000:00:00.5: port 3 timestamp id 0 [ 104.405601] mscc_felix 0000:00:00.5: port 3 timestamp id 0 [ 104.510624] mscc_felix 0000:00:00.5: port 3 timestamp id 0 ptp4l[104.965]: selected best master clock d858d7.fffe.00ca6d ptp4l[104.966]: port 1 (swp3): assuming the grand master role ptp4l[104.967]: port 1 (swp3): LISTENING to GRAND_MASTER on RS_GRAND_MASTER [ 105.106201] mscc_felix 0000:00:00.5: port 3 timestamp id 0 [ 105.232420] mscc_felix 0000:00:00.5: port 3 timestamp id 0 [ 105.359001] mscc_felix 0000:00:00.5: port 3 timestamp id 0 [ 105.405500] mscc_felix 0000:00:00.5: port 3 timestamp id 0 [ 105.485356] mscc_felix 0000:00:00.5: port 3 timestamp id 0 [ 105.511220] mscc_felix 0000:00:00.5: port 3 timestamp id 0 [ 105.610938] mscc_felix 0000:00:00.5: port 3 timestamp id 0 [ 105.737237] mscc_felix 0000:00:00.5: port 3 timestamp id 0 (...)
Notice that in this new usage pattern, a non-congested port should basically use timestamp ID 0 all the time, progressing to higher numbers only if there are unacknowledged timestamps in flight. Compare this to the old usage, where the timestamp ID used to monotonically increase modulo OCELOT_MAX_PTP_ID.
In terms of implementation, this simplifies the bookkeeping of the ocelot_port :: ts_id and ptp_skbs_in_flight. Since we need to traverse the list of two-step timestampable skbs for each new packet anyway, the information can already be computed and does not need to be stored. Also, ocelot_port->tx_skbs is always accessed under the switch-wide ocelot->ts_id_lock IRQ-unsafe spinlock, so we don't need the skb queue's lock and can use the unlocked primitives safely.
This problem was actually detected using the tc-taprio offload, and is causing trouble in TSN scenarios, which Felix (NXP LS1028A / VSC9959) supports but Ocelot (VSC7514) does not. Thus, I've selected the commit to blame as the one adding initial timestamping support for the Felix switch.
Fixes: c0bcf537667c ("net: dsa: ocelot: add hardware timestamping support for Felix") Signed-off-by: Vladimir Oltean vladimir.oltean@nxp.com Link: https://patch.msgid.link/20241205145519.1236778-5-vladimir.oltean@nxp.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/net/ethernet/mscc/ocelot_ptp.c | 134 +++++++++++++++---------- include/linux/dsa/ocelot.h | 1 + include/soc/mscc/ocelot.h | 2 - 3 files changed, 80 insertions(+), 57 deletions(-)
diff --git a/drivers/net/ethernet/mscc/ocelot_ptp.c b/drivers/net/ethernet/mscc/ocelot_ptp.c index c54e96ff3976..bc44aa635d49 100644 --- a/drivers/net/ethernet/mscc/ocelot_ptp.c +++ b/drivers/net/ethernet/mscc/ocelot_ptp.c @@ -14,6 +14,8 @@ #include <soc/mscc/ocelot.h> #include "ocelot.h"
+#define OCELOT_PTP_TX_TSTAMP_TIMEOUT (5 * HZ) + int ocelot_ptp_gettime64(struct ptp_clock_info *ptp, struct timespec64 *ts) { struct ocelot *ocelot = container_of(ptp, struct ocelot, ptp_info); @@ -607,34 +609,88 @@ int ocelot_get_ts_info(struct ocelot *ocelot, int port, } EXPORT_SYMBOL(ocelot_get_ts_info);
-static int ocelot_port_add_txtstamp_skb(struct ocelot *ocelot, int port, +static struct sk_buff *ocelot_port_dequeue_ptp_tx_skb(struct ocelot *ocelot, + int port, u8 ts_id, + u32 seqid) +{ + struct ocelot_port *ocelot_port = ocelot->ports[port]; + struct sk_buff *skb, *skb_tmp, *skb_match = NULL; + struct ptp_header *hdr; + + spin_lock(&ocelot->ts_id_lock); + + skb_queue_walk_safe(&ocelot_port->tx_skbs, skb, skb_tmp) { + if (OCELOT_SKB_CB(skb)->ts_id != ts_id) + continue; + + /* Check that the timestamp ID is for the expected PTP + * sequenceId. We don't have to test ptp_parse_header() against + * NULL, because we've pre-validated the packet's ptp_class. + */ + hdr = ptp_parse_header(skb, OCELOT_SKB_CB(skb)->ptp_class); + if (seqid != ntohs(hdr->sequence_id)) + continue; + + __skb_unlink(skb, &ocelot_port->tx_skbs); + ocelot->ptp_skbs_in_flight--; + skb_match = skb; + break; + } + + spin_unlock(&ocelot->ts_id_lock); + + return skb_match; +} + +static int ocelot_port_queue_ptp_tx_skb(struct ocelot *ocelot, int port, struct sk_buff *clone) { struct ocelot_port *ocelot_port = ocelot->ports[port]; + DECLARE_BITMAP(ts_id_in_flight, OCELOT_MAX_PTP_ID); + struct sk_buff *skb, *skb_tmp; + unsigned long n;
spin_lock(&ocelot->ts_id_lock);
- if (ocelot_port->ptp_skbs_in_flight == OCELOT_MAX_PTP_ID || - ocelot->ptp_skbs_in_flight == OCELOT_PTP_FIFO_SIZE) { + /* To get a better chance of acquiring a timestamp ID, first flush the + * stale packets still waiting in the TX timestamping queue. They are + * probably lost. + */ + skb_queue_walk_safe(&ocelot_port->tx_skbs, skb, skb_tmp) { + if (time_before(OCELOT_SKB_CB(skb)->ptp_tx_time + + OCELOT_PTP_TX_TSTAMP_TIMEOUT, jiffies)) { + dev_warn_ratelimited(ocelot->dev, + "port %d invalidating stale timestamp ID %u which seems lost\n", + port, OCELOT_SKB_CB(skb)->ts_id); + __skb_unlink(skb, &ocelot_port->tx_skbs); + kfree_skb(skb); + ocelot->ptp_skbs_in_flight--; + } else { + __set_bit(OCELOT_SKB_CB(skb)->ts_id, ts_id_in_flight); + } + } + + if (ocelot->ptp_skbs_in_flight == OCELOT_PTP_FIFO_SIZE) { spin_unlock(&ocelot->ts_id_lock); return -EBUSY; }
- skb_shinfo(clone)->tx_flags |= SKBTX_IN_PROGRESS; - /* Store timestamp ID in OCELOT_SKB_CB(clone)->ts_id */ - OCELOT_SKB_CB(clone)->ts_id = ocelot_port->ts_id; - - ocelot_port->ts_id++; - if (ocelot_port->ts_id == OCELOT_MAX_PTP_ID) - ocelot_port->ts_id = 0; + n = find_first_zero_bit(ts_id_in_flight, OCELOT_MAX_PTP_ID); + if (n == OCELOT_MAX_PTP_ID) { + spin_unlock(&ocelot->ts_id_lock); + return -EBUSY; + }
- ocelot_port->ptp_skbs_in_flight++; + /* Found an available timestamp ID, use it */ + OCELOT_SKB_CB(clone)->ts_id = n; + OCELOT_SKB_CB(clone)->ptp_tx_time = jiffies; ocelot->ptp_skbs_in_flight++; - - skb_queue_tail(&ocelot_port->tx_skbs, clone); + __skb_queue_tail(&ocelot_port->tx_skbs, clone);
spin_unlock(&ocelot->ts_id_lock);
+ dev_dbg_ratelimited(ocelot->dev, "port %d timestamp id %lu\n", port, n); + return 0; }
@@ -690,12 +746,14 @@ int ocelot_port_txtstamp_request(struct ocelot *ocelot, int port, if (!(*clone)) return -ENOMEM;
- err = ocelot_port_add_txtstamp_skb(ocelot, port, *clone); + /* Store timestamp ID in OCELOT_SKB_CB(clone)->ts_id */ + err = ocelot_port_queue_ptp_tx_skb(ocelot, port, *clone); if (err) { kfree_skb(*clone); return err; }
+ skb_shinfo(*clone)->tx_flags |= SKBTX_IN_PROGRESS; OCELOT_SKB_CB(skb)->ptp_cmd = ptp_cmd; OCELOT_SKB_CB(*clone)->ptp_class = ptp_class; } @@ -731,26 +789,14 @@ static void ocelot_get_hwtimestamp(struct ocelot *ocelot, spin_unlock_irqrestore(&ocelot->ptp_clock_lock, flags); }
-static bool ocelot_validate_ptp_skb(struct sk_buff *clone, u16 seqid) -{ - struct ptp_header *hdr; - - hdr = ptp_parse_header(clone, OCELOT_SKB_CB(clone)->ptp_class); - if (WARN_ON(!hdr)) - return false; - - return seqid == ntohs(hdr->sequence_id); -} - void ocelot_get_txtstamp(struct ocelot *ocelot) { int budget = OCELOT_PTP_QUEUE_SZ;
while (budget--) { - struct sk_buff *skb, *skb_tmp, *skb_match = NULL; struct skb_shared_hwtstamps shhwtstamps; u32 val, id, seqid, txport; - struct ocelot_port *port; + struct sk_buff *skb_match; struct timespec64 ts;
val = ocelot_read(ocelot, SYS_PTP_STATUS); @@ -766,36 +812,14 @@ void ocelot_get_txtstamp(struct ocelot *ocelot) txport = SYS_PTP_STATUS_PTP_MESS_TXPORT_X(val); seqid = SYS_PTP_STATUS_PTP_MESS_SEQ_ID(val);
- port = ocelot->ports[txport]; - - spin_lock(&ocelot->ts_id_lock); - port->ptp_skbs_in_flight--; - ocelot->ptp_skbs_in_flight--; - spin_unlock(&ocelot->ts_id_lock); - /* Retrieve its associated skb */ -try_again: - spin_lock(&port->tx_skbs.lock); - - skb_queue_walk_safe(&port->tx_skbs, skb, skb_tmp) { - if (OCELOT_SKB_CB(skb)->ts_id != id) - continue; - __skb_unlink(skb, &port->tx_skbs); - skb_match = skb; - break; - } - - spin_unlock(&port->tx_skbs.lock); - - if (WARN_ON(!skb_match)) + skb_match = ocelot_port_dequeue_ptp_tx_skb(ocelot, txport, id, + seqid); + if (!skb_match) { + dev_warn_ratelimited(ocelot->dev, + "port %d received TX timestamp (seqid %d, ts id %u) for packet previously declared stale\n", + txport, seqid, id); goto next_ts; - - if (!ocelot_validate_ptp_skb(skb_match, seqid)) { - dev_err_ratelimited(ocelot->dev, - "port %d received stale TX timestamp for seqid %d, discarding\n", - txport, seqid); - kfree_skb(skb); - goto try_again; }
/* Get the h/w timestamp */ diff --git a/include/linux/dsa/ocelot.h b/include/linux/dsa/ocelot.h index 6fbfbde68a37..620a3260fc08 100644 --- a/include/linux/dsa/ocelot.h +++ b/include/linux/dsa/ocelot.h @@ -15,6 +15,7 @@ struct ocelot_skb_cb { struct sk_buff *clone; unsigned int ptp_class; /* valid only for clones */ + unsigned long ptp_tx_time; /* valid only for clones */ u32 tstamp_lo; u8 ptp_cmd; u8 ts_id; diff --git a/include/soc/mscc/ocelot.h b/include/soc/mscc/ocelot.h index 846132ca5503..51d3e9ec5aa3 100644 --- a/include/soc/mscc/ocelot.h +++ b/include/soc/mscc/ocelot.h @@ -778,7 +778,6 @@ struct ocelot_port {
phy_interface_t phy_mode;
- unsigned int ptp_skbs_in_flight; struct sk_buff_head tx_skbs;
unsigned int trap_proto; @@ -786,7 +785,6 @@ struct ocelot_port { u16 mrp_ring_id;
u8 ptp_cmd; - u8 ts_id;
u8 index;