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Add support for enabling Tx timestamp requests for outgoing packets on E810 devices. The ice hardware can support multiple outstanding Tx timestamp requests. When sending a descriptor to hardware, a Tx timestamp request is made by setting a request bit, and assigning an index that represents which Tx timestamp index to store the timestamp in. Hardware makes no effort to synchronize the index use, so it is up to software to ensure that Tx timestamp indexes are not re-used before the timestamp is reported back. To do this, introduce a Tx timestamp tracker which will keep track of currently in-use indexes. In the hot path, if a packet has a timestamp request, an index will be requested from the tracker. Unfortunately, this does require a lock as the indexes are shared across all queues on a PHY. There are not enough indexes to reliably assign only 1 to each queue. For the E810 devices, the timestamp indexes are not shared across PHYs, so each port can have its own tracking. Once hardware captures a timestamp, an interrupt is fired. In this interrupt, trigger a new work item that will figure out which timestamp was completed, and report the timestamp back to the stack. This function loops through the Tx timestamp indexes and checks whether there is now a valid timestamp. If so, it clears the PHY timestamp indication in the PHY memory, locks and removes the SKB and bit in the tracker, then reports the timestamp to the stack. It is possible in some cases that a timestamp request will be initiated but never completed. This might occur if the packet is dropped by software or hardware before it reaches the PHY. Add a task to the periodic work function that will check whether a timestamp request is more than a few seconds old. If so, the timestamp index is cleared in the PHY, and the SKB is released. Just as with Rx timestamps, the Tx timestamps are only 40 bits wide, and use the same overall logic for extending to 64 bits of nanoseconds. With this change, E810 devices should be able to perform basic PTP functionality. Future changes will extend the support to cover the E822-based devices. Signed-off-by: Jacob Keller <jacob.e.keller@intel.com> Tested-by: Tony Brelinski <tonyx.brelinski@intel.com> Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.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.