The tx_timestamp_timeout configuration defines the number of
milliseconds to wait for a Tx timestamp from the kernel stack. This
delay is necessary as Tx timestamps are captured after a packet is sent
and reported back via the socket error queue.
The current default is to poll for up to 1 millisecond. In practice, it
turns out that this is not always enough time for hardware and software
to capture the timestamp and report it back. Some hardware designs
require reading timestamps over registers or other slow mechanisms.
This extra delay results in the timestamp not being sent back to
userspace within the default 1 millisecond polling time. If that occurs
the following can be seen from ptp4l:
ptp4l[4756.840]: timed out while polling for tx timestamp
ptp4l[4756.840]: increasing tx_timestamp_timeout may correct this issue,
but it is likely caused by a driver bug
ptp4l[4756.840]: port 1 (p2p1): send sync failed
ptp4l[4756.840]: port 1 (p2p1): MASTER to FAULTY on FAULT_DETECTED
(FT_UNSPECIFIED)
This can confuse users because it implies this is a bug, when the
correct solution in many cases is to just increase the timeout to
a slightly higher value.
Since we know this is a problem for many drivers and hardware designs,
lets increase the default timeout.
Note that a longer timeout should not affect setups which return the
timestamp quickly. On modern kernels, the poll() call will return once
the timestamp is reported back to the socket error queue. (On old
kernels around the 3.x era the poll will sleep for the full duration
before reporting the timestamp, but this is now quite an old kernel
release).
Signed-off-by: Jacob Keller <jacob.e.kel...@intel.com>
---
config.c | 2 +-
configs/default.cfg | 2 +-
ptp4l.8 | 2 +-
3 files changed, 3 insertions(+), 3 deletions(-)
diff --git a/config.c b/config.c
index 4472d3d9d6f9..d0f011c0e165 100644
--- a/config.c
+++ b/config.c
@@ -323,7 +323,7 @@ struct config_item config_tab[] = {
GLOB_ITEM_INT("ts2phc.pulsewidth", 500000000, 1000000, 999000000),
PORT_ITEM_ENU("tsproc_mode", TSPROC_FILTER, tsproc_enu),
GLOB_ITEM_INT("twoStepFlag", 1, 0, 1),
- GLOB_ITEM_INT("tx_timestamp_timeout", 1, 1, INT_MAX),
+ GLOB_ITEM_INT("tx_timestamp_timeout", 10, 1, INT_MAX),
PORT_ITEM_INT("udp_ttl", 1, 1, 255),
PORT_ITEM_INT("udp6_scope", 0x0E, 0x00, 0x0F),
GLOB_ITEM_STR("uds_address", "/var/run/ptp4l"),
diff --git a/configs/default.cfg b/configs/default.cfg
index 64ef3bd7c81d..d61561072334 100644
--- a/configs/default.cfg
+++ b/configs/default.cfg
@@ -51,7 +51,7 @@ hybrid_e2e 0
inhibit_multicast_service 0
net_sync_monitor 0
tc_spanning_tree 0
-tx_timestamp_timeout 1
+tx_timestamp_timeout 10
unicast_listen 0
unicast_master_table 0
unicast_req_duration 3600
diff --git a/ptp4l.8 b/ptp4l.8
index fe9e1502231c..7ca3474304e6 100644
--- a/ptp4l.8
+++ b/ptp4l.8
@@ -496,7 +496,7 @@ switches all implement this option together with the BMCA.
.B tx_timestamp_timeout
The number of milliseconds to poll waiting for the tx time stamp from the
kernel
when a message has recently been sent.
-The default is 1.
+The default is 10.
.TP
.B check_fup_sync
Because of packet reordering that can occur in the network, in the
--
2.31.1.331.gb0c09ab8796f
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