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1880bc4e4a
Transmitted packet timestamping accuracy can be improved when using timestamp from the port, instead of packet CQE creation timestamp, as it better reflects the actual time of a packet's transmit. TX port timestamping is supported starting from ConnectX6-DX hardware. Although at the original completion, only CQE timestamp can be attached, we are able to get TX port timestamping via an additional completion over a special CQ associated with the SQ (in addition to the regular CQ). Driver to ignore the original packet completion timestamp, and report back the timestamp of the special CQ completion. If the absolute timestamp diff between the two completions is greater than 1 / 128 second, ignore the TX port timestamp as it has a jitter which is too big. No skb will be generate out of the extra completion. Allocate additional CQ per ptpsq, to receive the TX port timestamp. Driver to hold an skb FIFO in order to map between transmitted skb to the two expected completions. When using ptpsq, hold double refcount on the skb, to gaurantee it will not get released before both completions arrive. Expose dedicated counters of the ptp additional CQ and connect it to the TX health reporter. This patch improves TX Hardware timestamping offset to be less than 40ns at a 100Gbps line rate, compared to 600ns before. With that, making our HW compliant with G.8273.2 class C, and allow Linux systems to be deployed in the 5G telco edge, where this standard is a must. Signed-off-by: Eran Ben Elisha <eranbe@nvidia.com> Reviewed-by: Tariq Toukan <tariqt@nvidia.com> Signed-off-by: Saeed Mahameed <saeedm@nvidia.com> |
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.