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In Store and Forward mode, flushing frames when the receive buffer is unavailable, can cause the MTL Rx FIFO to go out of sync. This results in buffering of a few frames in the FIFO without triggering Rx DMA from transferring the data to the system memory until another packet is received. Once the issue happens, for a ping request, the packet is forwarded to the system memory only after we receive another packet and hece we observe a latency equivalent to the ping interval. 64 bytes from 192.168.2.100: seq=1 ttl=64 time=1000.344 ms Also, we can observe constant gmacgrp_debug register value of 0x00000120, which indicates "Reading frame data". The issue is not reproducible after disabling frame flushing when Rx buffer is unavailable. But in that case, the Rx DMA enters a suspend state due to buffer unavailability. To resume operation, software must write to the receive_poll_demand register after adding new descriptors, which reactivates the Rx DMA. This issue is observed in the socfpga platforms which has dwmac1000 IP like Arria 10, Cyclone V and Agilex 7. Issue is reproducible after running iperf3 server at the DUT for UDP lower packet sizes. Signed-off-by: Rohan G Thomas <rohan.g.thomas@altera.com> Reviewed-by: Matthew Gerlach <matthew.gerlach@altera.com> Tested-by: Maxime Chevallier <maxime.chevallier@bootlin.com> Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk> Link: https://patch.msgid.link/20251126-a10_ext_fix-v1-1-d163507f646f@altera.com Signed-off-by: Paolo Abeni <pabeni@redhat.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.