commit 1a2dfe9b00b79a59acf905476bbc33c74d5770a3

Author: Jacob Keller <jacob.e.keller@intel.com>

Date:   Thu Jul 8 12:59:30 2021 -0700

    Increase the default tx_timestamp_timeout to 10

    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.keller@intel.com>

diff --git a/config.c b/config.c

index 760b395..03d981e 100644

--- a/config.c

+++ b/config.c

@@ -324,7 +324,7 @@ 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 64ef3bd..d615610 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 fe9e150..7ca3474 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