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In the ENETC receive path, a frame received by the MAC is first stored in a 256KB 'FIFO' memory, then transferred to DRAM when enqueuing it to the RX ring. The FIFO is a shared resource for all ENETC ports, but every port keeps track of its own memory utilization, on RX and on TX. There is a setting for RX rings through which they can either operate in 'lossy' mode (where the lack of a free buffer causes an immediate discard of the frame) or in 'lossless' mode (where the lack of a free buffer in the ring makes the frame stay longer in the FIFO). In turn, when the memory utilization of the FIFO exceeds a certain margin, the MAC can be configured to emit PAUSE frames. There is enough FIFO memory to buffer up to 3 MTU-sized frames per RX port while not jeopardizing the other use cases (jumbo frames), and also not consume bytes from the port TX allocations. Also, 3 MTU-sized frames worth of memory is enough to ensure zero loss for 64 byte packets at 1G line rate. Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com> Reviewed-by: Claudiu Manoil <claudiu.manoil@nxp.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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.