[PATCH v2] drivers: phy: Add Cortina CS4340 driver

[Bogdan Purcareata]

Add basic support for Cortina PHY drivers. Support only CS4340 for now.
The phys are not compatible with IEEE 802.3 clause 45 registers. Implement
proper read_status support, so that phy polling does not cause bus
register access errors.

The driver should be described using the "ethernet-phy-id" device tree
compatible.

Signed-off-by: Bogdan Purcareata <bogdan.purcareata@xxxxxxx>
---
v1 -> v2:
- Rename "mdio-cortina.c" to "cortina.c" since it's a phy driver.
- Test probing based on the "ethernet-phy-id" compatible. In the previous
  version, getting the phy_id via get_phy_c45_ids() involved an additional
  hack. Drop that approach and document probing in the commit message.

 drivers/net/phy/Kconfig   |  5 +++
 drivers/net/phy/Makefile  |  1 +
 drivers/net/phy/cortina.c | 90 +++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 96 insertions(+)
 create mode 100644 drivers/net/phy/cortina.c

diff --git a/drivers/net/phy/Kconfig b/drivers/net/phy/Kconfig
index 22dea7f..ad09e2d 100644
--- a/drivers/net/phy/Kconfig
+++ b/drivers/net/phy/Kconfig
@@ -240,6 +240,11 @@ config CICADA_PHY
 	---help---
 	  Currently supports the cis8204
 
+config CORTINA_PHY
+	tristate "Cortina quad-10G Ethernet PHY"
+	---help---
+	  Currently supports the CS4340 phy.
+
 config DAVICOM_PHY
 	tristate "Davicom PHYs"
 	---help---
diff --git a/drivers/net/phy/Makefile b/drivers/net/phy/Makefile
index 79365be..0de3e20 100644
--- a/drivers/net/phy/Makefile
+++ b/drivers/net/phy/Makefile
@@ -47,6 +47,7 @@ obj-$(CONFIG_BCM_CYGNUS_PHY)	+= bcm-cygnus.o
 obj-$(CONFIG_BCM_NET_PHYLIB)	+= bcm-phy-lib.o
 obj-$(CONFIG_BROADCOM_PHY)	+= broadcom.o
 obj-$(CONFIG_CICADA_PHY)	+= cicada.o
+obj-$(CONFIG_CORTINA_PHY)	+= cortina.o
 obj-$(CONFIG_DAVICOM_PHY)	+= davicom.o
 obj-$(CONFIG_DP83640_PHY)	+= dp83640.o
 obj-$(CONFIG_DP83848_PHY)	+= dp83848.o
diff --git a/drivers/net/phy/cortina.c b/drivers/net/phy/cortina.c
new file mode 100644
index 0000000..6f054ed
--- /dev/null
+++ b/drivers/net/phy/cortina.c
@@ -0,0 +1,90 @@
+/*
+ *    Based on code from Cortina Systems, Inc.
+ *
+ *    Copyright 2011 Cortina Systems, Inc.
+ *    Copyright 2017 NXP
+ *
+ *    This program is free software; you can redistribute it and/or modify
+ *    it under the terms of the GNU General Public License as published by
+ *    the Free Software Foundation; either version 2 of the License, or
+ *    (at your option) any later version.
+ *
+ *    This program is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    GNU General Public License for more details.
+ *
+ */
+#include <linux/module.h>
+#include <linux/phy.h>
+
+#define PHY_ID_CS4340	0x13e51002
+
+#define CORTINA_GPIO_GPIO_INTS				0x16D
+
+static int cortina_read_x(struct phy_device *phydev, int off, u16 regnum)
+{
+	return mdiobus_read(phydev->mdio.bus, phydev->mdio.addr + off,
+			    MII_ADDR_C45 | regnum);
+}
+
+static int cortina_read(struct phy_device *phydev, u16 regnum)
+{
+	return cortina_read_x(phydev, 0, regnum);
+}
+
+static int cortina_config_aneg(struct phy_device *phydev)
+{
+	phydev->supported = SUPPORTED_10000baseT_Full;
+	phydev->advertising = SUPPORTED_10000baseT_Full;
+
+	return 0;
+}
+
+static int cortina_read_status(struct phy_device *phydev)
+{
+	int gpio_int_status;
+	int ret = 0;
+
+	gpio_int_status = cortina_read(phydev, CORTINA_GPIO_GPIO_INTS);
+	if (gpio_int_status < 0) {
+		ret = gpio_int_status;
+		goto err;
+	}
+
+	if (gpio_int_status & 0x8) {
+		phydev->speed = SPEED_10000;
+		phydev->duplex = DUPLEX_FULL;
+		phydev->link = 1;
+	} else {
+		phydev->link = 0;
+	}
+
+err:
+	return ret;
+}
+
+static int cortina_soft_reset(struct phy_device *phydev)
+{
+	return 0;
+}
+
+static struct phy_driver cortina_driver[] = {
+{
+	.phy_id         = PHY_ID_CS4340,
+	.phy_id_mask    = 0xffffffff,
+	.name           = "Cortina CS4340",
+	.config_aneg    = cortina_config_aneg,
+	.read_status    = cortina_read_status,
+	.soft_reset     = cortina_soft_reset,
+},
+};
+
+module_phy_driver(cortina_driver);
+
+static struct mdio_device_id __maybe_unused cortina_tbl[] = {
+	{ PHY_ID_CS4340, 0xffffffff},
+	{},
+};
+
+MODULE_DEVICE_TABLE(mdio, cortina_tbl);
-- 
1.9.1