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E830 supports Earliest TxTime First (ETF) hardware offload, which is configured via the ETF Qdisc on a per-queue basis (see tc-etf(8)). ETF introduces a new Tx flow mechanism that utilizes a timestamp ring (tstamp_ring) alongside the standard Tx ring. This timestamp ring is used to indicate when hardware will transmit a packet. Tx Time is supported on the first 2048 Tx queues of the device, and the NVM image limits the maximum number of Tx queues to 2048 for the device. The allocation and initialization of the timestamp ring occur when the feature is enabled on a specific Tx queue via tc-etf. The requested Tx Time queue index cannot be greater than the number of Tx queues (vsi->num_txq). To support ETF, the following flags and bitmap are introduced: - ICE_F_TXTIME: Device feature flag set for E830 NICs, indicating ETF support. - txtime_txqs: PF-level bitmap set when ETF is enabled and cleared when disabled for a specific Tx queue. It is used by ice_is_txtime_ena() to check if ETF is allocated and configured on any Tx queue, which is checked during Tx ring allocation. - ICE_TX_FLAGS_TXTIME: Per Tx ring flag set when ETF is allocated and configured for a specific Tx queue. It determines ETF status during packet transmission and is checked by ice_is_txtime_ena() to verify if ETF is enabled on any Tx queue. Due to a hardware issue that can result in a malicious driver detection event, additional timestamp descriptors are required when wrapping around the timestamp ring. Up to 64 additional timestamp descriptors are reserved, reducing the available Tx descriptors. To accommodate this, ICE_MAX_NUM_DESC_BY_MAC is introduced, defining: - E830: Maximum Tx descriptor count of 8096 (8K - 32 - 64 for timestamp fetch descriptors). - E810 and E82X: Maximum Tx descriptor count of 8160 (8K - 32). Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com> Co-developed-by: Alice Michael <alice.michael@intel.com> Signed-off-by: Alice Michael <alice.michael@intel.com> Signed-off-by: Paul Greenwalt <paul.greenwalt@intel.com> Acked-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com> Tested-by: Rinitha S <sx.rinitha@intel.com> (A Contingent worker at Intel) Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
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 reStructuredText 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.