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As described by the microchip article "LAN937X - The required configuration for the external MAC port to operate at RGMII-to-RGMII 1Gbps link speed." [1]: "When VPHY is enabled, the auto-negotiation process following IEEE 802.3 standard will be triggered and will result in RGMII-to-RGMII signal failure on the interface because VPHY will try to poll the PHY status that is not available in the scenario of RGMII-to-RGMII connection (normally the link partner is usually an external processor). Note that when VPHY fails on accessing PHY registers, it will fall back to 100Mbps speed, it indicates disabling VPHY is optional if you only need the port to link at 100Mbps speed. Again, VPHY must and can only be disabled by writing VPHY_DISABLE bit in the register below as there is no strapping pin for the control." This patch was tested on LAN9372, so far it seems to not to affect VPHY based clock crossing optimization for the ports with integrated PHYs. [1]: https://microchip.my.site.com/s/article/LAN937X-The-required-configuration-for-the-external-MAC-port-to-operate-at-RGMII-to-RGMII-1Gbps-link-speed Signed-off-by: Lucas Stach <l.stach@pengutronix.de> Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de> Reviewed-by: Vladimir Oltean <olteanv@gmail.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 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.