net: phy: Add Synopsys DesignWare XPCS MDIO module

Synopsys DesignWare XPCS is an MMD that can manage link status,
auto-negotiation, link training, ...

In this commit we add basic support for XPCS using USXGMII interface and
Clause 73 Auto-negotiation.

This is highly tied with PHYLINK and can't be used without it. A given
ethernet driver can use the provided callbacks to add the support for
XPCS.

Signed-off-by: Jose Abreu <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

Author: joabreu

MAINTAINERS

@@ -16117,6 +16117,13 @@ L:	[email protected]
 S:	Supported
 F:	drivers/net/ethernet/synopsys/
 
+SYNOPSYS DESIGNWARE ETHERNET XPCS DRIVER
+M:	Jose Abreu <[email protected]>
+L:	[email protected]
+S:	Supported
+F:	drivers/net/phy/mdio-xpcs.c
+F:	include/linux/mdio-xpcs.h
+
 SYNOPSYS DESIGNWARE I2C DRIVER
 M:	Jarkko Nikula <[email protected]>
 R:	Andy Shevchenko <[email protected]>

drivers/net/phy/Kconfig

@@ -214,6 +214,12 @@ config MDIO_XGENE
 	  This module provides a driver for the MDIO busses found in the
 	  APM X-Gene SoC's.
 
+config MDIO_XPCS
+	tristate "Synopsys DesignWare XPCS controller"
+	help
+	  This module provides helper functions for Synopsys DesignWare XPCS
+	  controllers.
+
 endif
 endif
 

drivers/net/phy/Makefile

@@ -44,6 +44,7 @@ obj-$(CONFIG_MDIO_OCTEON)	+= mdio-octeon.o
 obj-$(CONFIG_MDIO_SUN4I)	+= mdio-sun4i.o
 obj-$(CONFIG_MDIO_THUNDER)	+= mdio-thunder.o
 obj-$(CONFIG_MDIO_XGENE)	+= mdio-xgene.o
+obj-$(CONFIG_MDIO_XPCS)		+= mdio-xpcs.o
 
 obj-$(CONFIG_NETWORK_PHY_TIMESTAMPING) += mii_timestamper.o