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commit 1a2dfe9b00b79a59acf905476bbc33c74d5770a3
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Author: Jacob Keller <jacob.e.keller@intel.com>
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Date: Thu Jul 8 12:59:30 2021 -0700
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Increase the default tx_timestamp_timeout to 10
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The tx_timestamp_timeout configuration defines the number of
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milliseconds to wait for a Tx timestamp from the kernel stack. This
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delay is necessary as Tx timestamps are captured after a packet is sent
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and reported back via the socket error queue.
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The current default is to poll for up to 1 millisecond. In practice, it
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turns out that this is not always enough time for hardware and software
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to capture the timestamp and report it back. Some hardware designs
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require reading timestamps over registers or other slow mechanisms.
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This extra delay results in the timestamp not being sent back to
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userspace within the default 1 millisecond polling time. If that occurs
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the following can be seen from ptp4l:
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ptp4l[4756.840]: timed out while polling for tx timestamp
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ptp4l[4756.840]: increasing tx_timestamp_timeout may correct this issue,
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but it is likely caused by a driver bug
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ptp4l[4756.840]: port 1 (p2p1): send sync failed
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ptp4l[4756.840]: port 1 (p2p1): MASTER to FAULTY on FAULT_DETECTED
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(FT_UNSPECIFIED)
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This can confuse users because it implies this is a bug, when the
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correct solution in many cases is to just increase the timeout to
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a slightly higher value.
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Since we know this is a problem for many drivers and hardware designs,
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lets increase the default timeout.
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Note that a longer timeout should not affect setups which return the
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timestamp quickly. On modern kernels, the poll() call will return once
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the timestamp is reported back to the socket error queue. (On old
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kernels around the 3.x era the poll will sleep for the full duration
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before reporting the timestamp, but this is now quite an old kernel
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release).
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Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
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diff --git a/config.c b/config.c
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index 760b395..03d981e 100644
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--- a/config.c
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+++ b/config.c
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@@ -324,7 +324,7 @@ struct config_item config_tab[] = {
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GLOB_ITEM_INT("ts2phc.pulsewidth", 500000000, 1000000, 999000000),
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PORT_ITEM_ENU("tsproc_mode", TSPROC_FILTER, tsproc_enu),
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GLOB_ITEM_INT("twoStepFlag", 1, 0, 1),
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- GLOB_ITEM_INT("tx_timestamp_timeout", 1, 1, INT_MAX),
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+ GLOB_ITEM_INT("tx_timestamp_timeout", 10, 1, INT_MAX),
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PORT_ITEM_INT("udp_ttl", 1, 1, 255),
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PORT_ITEM_INT("udp6_scope", 0x0E, 0x00, 0x0F),
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GLOB_ITEM_STR("uds_address", "/var/run/ptp4l"),
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diff --git a/configs/default.cfg b/configs/default.cfg
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index 64ef3bd..d615610 100644
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--- a/configs/default.cfg
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+++ b/configs/default.cfg
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@@ -51,7 +51,7 @@ hybrid_e2e 0
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inhibit_multicast_service 0
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net_sync_monitor 0
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tc_spanning_tree 0
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-tx_timestamp_timeout 1
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+tx_timestamp_timeout 10
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unicast_listen 0
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unicast_master_table 0
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unicast_req_duration 3600
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diff --git a/ptp4l.8 b/ptp4l.8
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index fe9e150..7ca3474 100644
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--- a/ptp4l.8
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+++ b/ptp4l.8
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@@ -496,7 +496,7 @@ switches all implement this option together with the BMCA.
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.B tx_timestamp_timeout
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The number of milliseconds to poll waiting for the tx time stamp from the kernel
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when a message has recently been sent.
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-The default is 1.
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+The default is 10.
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.TP
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.B check_fup_sync
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Because of packet reordering that can occur in the network, in the
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