net: phy: Introduce QUSGMII PHY mode
The QUSGMII mode is a derivative of Cisco's USXGMII standard. This standard is pretty similar to SGMII, but allows for faster speeds, and has the build-in bits for Quad and Octa variants (like QSGMII). The main difference with SGMII/QSGMII is that USXGMII/QUSGMII re-uses the preamble to carry various information, named 'Extensions'. As of today, the USXGMII standard only mentions the "PCH" extension, which is used to convey timestamps, allowing in-band signaling of PTP timestamps without having to modify the frame itself. This commit adds support for that mode. When no extension is in use, it behaves exactly like QSGMII, although it's not compatible with QSGMII. Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com> Reviewed-by: Andrew Lunn <andrew@lunn.ch> Signed-off-by: David S. Miller <davem@davemloft.net>
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