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authorMaxime Chevallier <maxime.chevallier@bootlin.com>2022-08-17 15:32:52 +0300
committerDavid S. Miller <davem@davemloft.net>2022-08-22 15:46:26 +0300
commit5e61fe157a27afc7c0d4f7bcbceefdca536c015f (patch)
treed4874661c2eba4a5c5643f0f123c653bc87987a5 /Documentation/networking
parentd04807b80691c6041ca8e3dcf1870d1bf1082c22 (diff)
downloadlinux-5e61fe157a27afc7c0d4f7bcbceefdca536c015f.tar.xz
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>
Diffstat (limited to 'Documentation/networking')
-rw-r--r--Documentation/networking/phy.rst9
1 files changed, 9 insertions, 0 deletions
diff --git a/Documentation/networking/phy.rst b/Documentation/networking/phy.rst
index 704f31da5167..712e44caebd0 100644
--- a/Documentation/networking/phy.rst
+++ b/Documentation/networking/phy.rst
@@ -308,6 +308,15 @@ Some of the interface modes are described below:
rate of 125Mpbs using a 4B/5B encoding scheme, resulting in an underlying
data rate of 100Mpbs.
+``PHY_INTERFACE_MODE_QUSGMII``
+ This defines the Cisco the Quad USGMII mode, which is the Quad variant of
+ the USGMII (Universal SGMII) link. It's very similar to QSGMII, but uses
+ a Packet Control Header (PCH) instead of the 7 bytes preamble to carry not
+ only the port id, but also so-called "extensions". The only documented
+ extension so-far in the specification is the inclusion of timestamps, for
+ PTP-enabled PHYs. This mode isn't compatible with QSGMII, but offers the
+ same capabilities in terms of link speed and negociation.
+
Pause frames / flow control
===========================