Add a Lynx PCS module which exposes the necessary operations to drive
the PCS using PHYLINK.

The majority of the code is extracted from the Felix DSA driver, which
will be also modified in a later patch, and exposed as a separate module
for code reusability purposes.

At the moment, USXGMII (only with in-band AN and speeds up to 2500),
SGMII, QSGMII and 2500Base-X (only w/o in-band AN) are supported by the
Lynx PCS module since these were also supported by Felix.

The module can only be enabled by the drivers in need and not user
selectable.

Signed-off-by: Ioana Ciornei <ioana.ciornei@nxp.com>
---
Changes in v2:
 * got rid of the mdio_lynx_pcs structure and directly exported the
 functions without the need of an indirection
 * solved the broken allmodconfig build test by making the module
 tristate instead of bool

Changes in v3:
 * renamed the file to pcs-lynx.c


 MAINTAINERS                |   7 +
 drivers/net/phy/Kconfig    |   6 +
 drivers/net/phy/Makefile   |   1 +
 drivers/net/phy/pcs-lynx.c | 337 +++++++++++++++++++++++++++++++++++++
 include/linux/pcs-lynx.h   |  25 +++
 5 files changed, 376 insertions(+)
 create mode 100644 drivers/net/phy/pcs-lynx.c
 create mode 100644 include/linux/pcs-lynx.h

diff --git a/MAINTAINERS b/MAINTAINERS
index 301330e02bca..850d8b4f2d29 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS

@@ -10168,6 +10168,13 @@ S:	Maintained
 W:	http://linux-test-project.github.io/
 T:	git git://github.com/linux-test-project/ltp.git
 
+LYNX PCS MODULE
+M:	Ioana Ciornei <ioana.ciornei@nxp.com>
+L:	netdev@vger.kernel.org
+S:	Maintained
+F:	drivers/net/phy/pcs-lynx.c
+F:	include/linux/pcs-lynx.h
+
 M68K ARCHITECTURE
 M:	Geert Uytterhoeven <geert@linux-m68k.org>
 L:	linux-m68k@lists.linux-m68k.org

diff --git a/drivers/net/phy/Kconfig b/drivers/net/phy/Kconfig
index f25702386d83..3a573afb21a3 100644
--- a/drivers/net/phy/Kconfig
+++ b/drivers/net/phy/Kconfig

@@ -235,6 +235,12 @@ config MDIO_XPCS
 	  This module provides helper functions for Synopsys DesignWare XPCS
 	  controllers.
 
+config PCS_LYNX
+	tristate
+	help
+	  This module provides helper functions for Lynx PCS enablement
+	  representing the PCS as an MDIO device.
+
 endif
 endif
 

diff --git a/drivers/net/phy/Makefile b/drivers/net/phy/Makefile
index dc9e53b511d6..15ea3345fe3c 100644
--- a/drivers/net/phy/Makefile
+++ b/drivers/net/phy/Makefile

@@ -47,6 +47,7 @@ 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_PCS_LYNX)		+= pcs-lynx.o
 
 obj-$(CONFIG_NETWORK_PHY_TIMESTAMPING) += mii_timestamper.o
 

diff --git a/drivers/net/phy/pcs-lynx.c b/drivers/net/phy/pcs-lynx.c
new file mode 100644
index 000000000000..23bdd9db4340
--- /dev/null
+++ b/drivers/net/phy/pcs-lynx.c

@@ -0,0 +1,337 @@
+// SPDX-License-Identifier: (GPL-2.0+ OR BSD-3-Clause)
+/* Copyright 2020 NXP
+ * Lynx PCS MDIO helpers
+ */
+
+#include <linux/mdio.h>
+#include <linux/phylink.h>
+#include <linux/pcs-lynx.h>
+
+#define SGMII_CLOCK_PERIOD_NS		8 /* PCS is clocked at 125 MHz */
+#define SGMII_LINK_TIMER_VAL(ns)	((u32)((ns) / SGMII_CLOCK_PERIOD_NS))
+
+#define SGMII_AN_LINK_TIMER_NS		1600000 /* defined by SGMII spec */
+
+#define SGMII_LINK_TIMER_LO		0x12
+#define SGMII_LINK_TIMER_HI		0x13
+#define SGMII_IF_MODE			0x14
+#define SGMII_IF_MODE_SGMII_EN		BIT(0)
+#define SGMII_IF_MODE_USE_SGMII_AN	BIT(1)
+#define SGMII_IF_MODE_SPEED(x)		(((x) << 2) & GENMASK(3, 2))
+#define SGMII_IF_MODE_SPEED_MSK		GENMASK(3, 2)
+#define SGMII_IF_MODE_DUPLEX		BIT(4)

+
+	if_mode = SGMII_IF_MODE_SGMII_EN;
+	if (mode == MLO_AN_INBAND) {
+		u32 link_timer;
+
+		if_mode |= SGMII_IF_MODE_USE_SGMII_AN;
+
+		/* Adjust link timer for SGMII */
+		link_timer = SGMII_LINK_TIMER_VAL(SGMII_AN_LINK_TIMER_NS);
+		mdiobus_write(bus, addr, SGMII_LINK_TIMER_LO, link_timer & 0xffff);
+		mdiobus_write(bus, addr, SGMII_LINK_TIMER_HI, link_timer >> 16);
+	}
+	mdiobus_modify(bus, addr, SGMII_IF_MODE,
+		       SGMII_IF_MODE_SGMII_EN | SGMII_IF_MODE_USE_SGMII_AN,
+		       if_mode);
+
+	err = phylink_mii_c22_pcs_config(pcs, mode, PHY_INTERFACE_MODE_SGMII,
+					 advertising);
+	return err;
+}
+
+static int lynx_pcs_config_usxgmii(struct mdio_device *pcs, unsigned int mode,
+				   const unsigned long *advertising)
+{
+	struct mii_bus *bus = pcs->bus;
+	int addr = pcs->addr;
+
+	/* Configure device ability for the USXGMII Replicator */
+	mdiobus_c45_write(bus, addr, MDIO_MMD_VEND2, MII_ADVERTISE,
+			  USXGMII_ADVERTISE_SPEED(USXGMII_SPEED_2500) |
+			  USXGMII_ADVERTISE_LSTATUS(1) |
+			  ADVERTISE_SGMII |
+			  ADVERTISE_LPACK |
+			  USXGMII_ADVERTISE_FDX);
+	return 0;
+}
+
+int lynx_pcs_config(struct mdio_device *pcs, unsigned int mode,
+		    phy_interface_t ifmode,
+		    const unsigned long *advertising)
+{
+	switch (ifmode) {
+	case PHY_INTERFACE_MODE_SGMII:
+	case PHY_INTERFACE_MODE_QSGMII:
+		lynx_pcs_config_sgmii(pcs, mode, advertising);
+		break;
+	case PHY_INTERFACE_MODE_2500BASEX:
+		/* 2500Base-X only works without in-band AN,
+		 * thus nothing to do here
+		 */
+		break;
+	case PHY_INTERFACE_MODE_USXGMII:
+		lynx_pcs_config_usxgmii(pcs, mode, advertising);
+		break;
+	default:
+		return -EOPNOTSUPP;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL(lynx_pcs_config);
+
+static void lynx_pcs_link_up_sgmii(struct mdio_device *pcs, unsigned int mode,
+				   int speed, int duplex)
+{
+	struct mii_bus *bus = pcs->bus;
+	u16 if_mode = 0, sgmii_speed;
+	int addr = pcs->addr;
+
+	/* The PCS needs to be configured manually only
+	 * when not operating on in-band mode
+	 */
+	if (mode == MLO_AN_INBAND)
+		return;
+
+	if (duplex == DUPLEX_HALF)
+		if_mode |= SGMII_IF_MODE_DUPLEX;
+
+	switch (speed) {
+	case SPEED_1000:
+		sgmii_speed = SGMII_SPEED_1000;
+		break;
+	case SPEED_100:
+		sgmii_speed = SGMII_SPEED_100;
+		break;
+	case SPEED_10:
+		sgmii_speed = SGMII_SPEED_10;
+		break;
+	case SPEED_UNKNOWN:
+		/* Silently don't do anything */
+		return;
+	default:
+		dev_err(&pcs->dev, "Invalid PCS speed %d\n", speed);
+		return;
+	}
+	if_mode |= SGMII_IF_MODE_SPEED(sgmii_speed);
+
+	mdiobus_modify(bus, addr, SGMII_IF_MODE,
+		       SGMII_IF_MODE_DUPLEX | SGMII_IF_MODE_SPEED_MSK,
+		       if_mode);
+}
+
+/* 2500Base-X is SerDes protocol 7 on Felix and 6 on ENETC. It is a SerDes lane
+ * clocked at 3.125 GHz which encodes symbols with 8b/10b and does not have
+ * auto-negotiation of any link parameters. Electrically it is compatible with
+ * a single lane of XAUI.
+ * The hardware reference manual wants to call this mode SGMII, but it isn't
+ * really, since the fundamental features of SGMII:
+ * - Downgrading the link speed by duplicating symbols
+ * - Auto-negotiation
+ * are not there.
+ * The speed is configured at 1000 in the IF_MODE because the clock frequency
+ * is actually given by a PLL configured in the Reset Configuration Word (RCW).
+ * Since there is no difference between fixed speed SGMII w/o AN and 802.3z w/o
+ * AN, we call this PHY interface type 2500Base-X. In case a PHY negotiates a
+ * lower link speed on line side, the system-side interface remains fixed at
+ * 2500 Mbps and we do rate adaptation through pause frames.
+ */
+static void lynx_pcs_link_up_2500basex(struct mdio_device *pcs,
+				       unsigned int mode,
+				       int speed, int duplex)
+{
+	struct mii_bus *bus = pcs->bus;
+	int addr = pcs->addr;
+
+	if (mode == MLO_AN_INBAND) {
+		dev_err(&pcs->dev, "AN not supported for 2500BaseX\n");
+		return;
+	}
+
+	mdiobus_write(bus, addr, SGMII_IF_MODE,
+		      SGMII_IF_MODE_SGMII_EN |
+		      SGMII_IF_MODE_SPEED(SGMII_SPEED_2500));
+}
+
+void lynx_pcs_link_up(struct mdio_device *pcs, unsigned int mode,
+		      phy_interface_t interface,
+		      int speed, int duplex)
+{
+	switch (interface) {
+	case PHY_INTERFACE_MODE_SGMII:
+	case PHY_INTERFACE_MODE_QSGMII:
+		lynx_pcs_link_up_sgmii(pcs, mode, speed, duplex);
+		break;
+	case PHY_INTERFACE_MODE_2500BASEX:
+		lynx_pcs_link_up_2500basex(pcs, mode, speed, duplex);
+		break;
+	case PHY_INTERFACE_MODE_USXGMII:
+		/* At the moment, only in-band AN is supported for USXGMII
+		 * so nothing to do in link_up
+		 */
+		break;
+	default:
+		break;
+	}
+}
+EXPORT_SYMBOL(lynx_pcs_link_up);
+
+MODULE_LICENSE("Dual BSD/GPL");

diff --git a/include/linux/pcs-lynx.h b/include/linux/pcs-lynx.h
new file mode 100644
index 000000000000..336fccb8c55f
--- /dev/null
+++ b/include/linux/pcs-lynx.h

@@ -0,0 +1,25 @@
+/* SPDX-License-Identifier: (GPL-2.0+ OR BSD-3-Clause) */
+/* Copyright 2020 NXP
+ * Lynx PCS helpers
+ */
+
+#ifndef __LINUX_PCS_LYNX_H
+#define __LINUX_PCS_LYNX_H
+
+#include <linux/phy.h>
+#include <linux/mdio.h>
+
+void lynx_pcs_an_restart(struct mdio_device *pcs, phy_interface_t ifmode);
+
+void lynx_pcs_get_state(struct mdio_device *pcs, phy_interface_t ifmode,
+			struct phylink_link_state *state);
+
+int lynx_pcs_config(struct mdio_device *pcs, unsigned int mode,
+		    phy_interface_t ifmode,
+		    const unsigned long *advertising);
+
+void lynx_pcs_link_up(struct mdio_device *pcs, unsigned int mode,
+		      phy_interface_t interface,
+		      int speed, int duplex);
+
+#endif /* __LINUX_PCS_LYNX_H */

-- 
2.25.1