diff options
| author | Pauli Virtanen <pav@iki.fi> | 2025-03-18 21:06:42 +0200 |
|---|---|---|
| committer | Luiz Augusto von Dentz <luiz.von.dentz@intel.com> | 2025-03-25 12:48:05 -0400 |
| commit | 983e0e4e87bdf465e8424b1902e41bfe51ba128a (patch) | |
| tree | 599b5d17f526ff34ac471ddaf393e19489bc3e2d /Documentation/networking | |
| parent | b257e02ecc46f8561d8bd88943164a10c9e90a80 (diff) | |
net-timestamp: COMPLETION timestamp on packet tx completion
Add SOF_TIMESTAMPING_TX_COMPLETION, for requesting a software timestamp
when hardware reports a packet completed.
Completion tstamp is useful for Bluetooth, as hardware timestamps do not
exist in the HCI specification except for ISO packets, and the hardware
has a queue where packets may wait. In this case the software SND
timestamp only reflects the kernel-side part of the total latency
(usually small) and queue length (usually 0 unless HW buffers
congested), whereas the completion report time is more informative of
the true latency.
It may also be useful in other cases where HW TX timestamps cannot be
obtained and user wants to estimate an upper bound to when the TX
probably happened.
Signed-off-by: Pauli Virtanen <pav@iki.fi>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Diffstat (limited to 'Documentation/networking')
| -rw-r--r-- | Documentation/networking/timestamping.rst | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/Documentation/networking/timestamping.rst b/Documentation/networking/timestamping.rst index 61ef9da10e28..b8fef8101176 100644 --- a/Documentation/networking/timestamping.rst +++ b/Documentation/networking/timestamping.rst @@ -140,6 +140,14 @@ SOF_TIMESTAMPING_TX_ACK: cumulative acknowledgment. The mechanism ignores SACK and FACK. This flag can be enabled via both socket options and control messages. +SOF_TIMESTAMPING_TX_COMPLETION: + Request tx timestamps on packet tx completion. The completion + timestamp is generated by the kernel when it receives packet a + completion report from the hardware. Hardware may report multiple + packets at once, and completion timestamps reflect the timing of the + report and not actual tx time. This flag can be enabled via both + socket options and control messages. + 1.3.2 Timestamp Reporting ^^^^^^^^^^^^^^^^^^^^^^^^^ |