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 <Jose.Abreu@synopsys.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

MAINTAINERS

@@ -16117,6 +16117,13 @@ L:	netdev@vger.kernel.org
 S:	Supported
 F:	drivers/net/ethernet/synopsys/
 
+SYNOPSYS DESIGNWARE ETHERNET XPCS DRIVER
+M:	Jose Abreu <Jose.Abreu@synopsys.com>
+L:	netdev@vger.kernel.org
+S:	Supported
+F:	drivers/net/phy/mdio-xpcs.c
+F:	include/linux/mdio-xpcs.h
+
 SYNOPSYS DESIGNWARE I2C DRIVER
 M:	Jarkko Nikula <jarkko.nikula@linux.intel.com>
 R:	Andy Shevchenko <andriy.shevchenko@linux.intel.com>

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
 

include/linux/mdio-xpcs.h

+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (c) 2020 Synopsys, Inc. and/or its affiliates.
+ * Synopsys DesignWare XPCS helpers
+ */
+
+#ifndef __LINUX_MDIO_XPCS_H
+#define __LINUX_MDIO_XPCS_H
+
+#include <linux/phy.h>
+#include <linux/phylink.h>
+
+struct mdio_xpcs_args {
+	__ETHTOOL_DECLARE_LINK_MODE_MASK(supported);
+	struct mii_bus *bus;
+	int addr;
+};
+
+struct mdio_xpcs_ops {
+	int (*validate)(struct mdio_xpcs_args *xpcs,
+			unsigned long *supported,
+			struct phylink_link_state *state);
+	int (*config)(struct mdio_xpcs_args *xpcs,
+		      const struct phylink_link_state *state);
+	int (*get_state)(struct mdio_xpcs_args *xpcs,
+			 struct phylink_link_state *state);
+	int (*link_up)(struct mdio_xpcs_args *xpcs, int speed,
+		       phy_interface_t interface);
+	int (*probe)(struct mdio_xpcs_args *xpcs, phy_interface_t interface);
+};
+
+#if IS_ENABLED(CONFIG_MDIO_XPCS)
+struct mdio_xpcs_ops *mdio_xpcs_get_ops(void);
+#else
+static inline struct mdio_xpcs_ops *mdio_xpcs_get_ops(void)
+{
+	return NULL;
+}
+#endif
+
+#endif /* __LINUX_MDIO_XPCS_H */