drivers/net/phy: add driver for the onsemi NCN26000 10BASE-T1S PHY

Add support for the onsemi NCN26000 10BASE-T1S industrial Ethernet PHY.
The driver supports Point-to-Multipoint operation without
auto-negotiation and with link control handling. The PLCA RS support
will be included on a separate patch.

Signed-off-by: Piergiorgio Beruto <piergiorgio.beruto@gmail.com>

MAINTAINERS

@@ -15357,6 +15357,13 @@ L:	linux-mips@vger.kernel.org
 S:	Maintained
 F:	arch/mips/boot/dts/ralink/omega2p.dts
 
+ONSEMI ETHERNET PHY DRIVERS
+M:	Piergiorgio Beruto <piergiorgio.beruto@gmail.com>
+L:	netdev@vger.kernel.org
+S:	Supported
+W:	http://www.onsemi.com
+F:	drivers/net/phy/ncn*
+
 OP-TEE DRIVER
 M:	Jens Wiklander <jens.wiklander@linaro.org>
 L:	op-tee@lists.trustedfirmware.org
@@ -16400,6 +16407,7 @@ PLCA RECONCILIATION SUBLAYER (IEEE802.3 Clause 148)
 M:	Piergiorgio Beruto <piergiorgio.beruto@gmail.com>
 L:	netdev@vger.kernel.org
 S:	Maintained
+F:	drivers/net/phy/mdio-open-alliance.h
 F:	net/ethtool/plca.c
 
 PLDMFW LIBRARY

drivers/net/phy/Kconfig

@@ -267,6 +267,13 @@ config NATIONAL_PHY
 	help
 	  Currently supports the DP83865 PHY.
 
+config NCN26000_PHY
+	tristate "onsemi 10BASE-T1S Ethernet PHY"
+	help
+	  Adds support for the onsemi 10BASE-T1S Ethernet PHY.
+	  Currently supports the NCN26000 10BASE-T1S Industrial PHY
+	  with MII interface.
+
 config NXP_C45_TJA11XX_PHY
 	tristate "NXP C45 TJA11XX PHYs"
 	depends on PTP_1588_CLOCK_OPTIONAL

drivers/net/phy/Makefile

@@ -77,6 +77,7 @@ obj-$(CONFIG_MICROCHIP_T1_PHY)	+= microchip_t1.o
 obj-$(CONFIG_MICROSEMI_PHY)	+= mscc/
 obj-$(CONFIG_MOTORCOMM_PHY)	+= motorcomm.o
 obj-$(CONFIG_NATIONAL_PHY)	+= national.o
+obj-$(CONFIG_NCN26000_PHY)	+= ncn26000.o
 obj-$(CONFIG_NXP_C45_TJA11XX_PHY)	+= nxp-c45-tja11xx.o
 obj-$(CONFIG_NXP_TJA11XX_PHY)	+= nxp-tja11xx.o
 obj-$(CONFIG_QSEMI_PHY)		+= qsemi.o

drivers/net/phy/mdio-open-alliance.h

@@ -0,0 +1,44 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * mdio-open-alliance.h - definition of OPEN Alliance SIG standard registers
+ */
+
+#ifndef __MDIO_OPEN_ALLIANCE__
+#define __MDIO_OPEN_ALLIANCE__
+
+#include <linux/mdio.h>
+
+/* MDIO Manageable Devices (MMDs). */
+#define MDIO_MMD_OATC14		MDIO_MMD_VEND2
+
+/* Open Alliance TC14 (10BASE-T1S) registers */
+#define MDIO_OATC14_PLCA_IDVER	0xca00  /* PLCA ID and version */
+#define MDIO_OATC14_PLCA_CTRL0	0xca01	/* PLCA Control register 0 */
+#define MDIO_OATC14_PLCA_CTRL1	0xca02	/* PLCA Control register 1 */
+#define MDIO_OATC14_PLCA_STATUS	0xca03	/* PLCA Status register */
+#define MDIO_OATC14_PLCA_TOTMR	0xca04	/* PLCA TO Timer register */
+#define MDIO_OATC14_PLCA_BURST	0xca05	/* PLCA BURST mode register */
+
+/* Open Alliance TC14 PLCA IDVER register */
+#define MDIO_OATC14_PLCA_IDM	0xff00	/* PLCA MAP ID */
+#define MDIO_OATC14_PLCA_VER	0x00ff	/* PLCA MAP version */
+
+/* Open Alliance TC14 PLCA CTRL0 register */
+#define MDIO_OATC14_PLCA_EN	0x8000  /* PLCA enable */
+#define MDIO_OATC14_PLCA_RST	0x4000  /* PLCA reset */
+
+/* Open Alliance TC14 PLCA CTRL1 register */
+#define MDIO_OATC14_PLCA_NCNT	0xff00	/* PLCA node count */
+#define MDIO_OATC14_PLCA_ID	0x00ff	/* PLCA local node ID */
+
+/* Open Alliance TC14 PLCA STATUS register */
+#define MDIO_OATC14_PLCA_PST	0x8000	/* PLCA status indication */
+
+/* Open Alliance TC14 PLCA TOTMR register */
+#define MDIO_OATC14_PLCA_TOT	0x00ff
+
+/* Open Alliance TC14 PLCA BURST register */
+#define MDIO_OATC14_PLCA_MAXBC	0xff00
+#define MDIO_OATC14_PLCA_BTMR	0x00ff
+
+#endif /* __MDIO_OPEN_ALLIANCE__ */

drivers/net/phy/ncn26000.c

@@ -0,0 +1,187 @@
+// SPDX-License-Identifier: (GPL-2.0+ OR BSD-3-Clause)
+/*
+ *  Driver for the onsemi 10BASE-T1S NCN26000 PHYs family.
+ *
+ * Copyright 2022 onsemi
+ */
+#include <linux/kernel.h>
+#include <linux/bitfield.h>
+#include <linux/errno.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/mii.h>
+#include <linux/phy.h>
+
+#include "mdio-open-alliance.h"
+
+#define PHY_ID_NCN26000			0x180FF5A1
+
+#define NCN26000_REG_IRQ_CTL            16
+#define NCN26000_REG_IRQ_STATUS         17
+
+// the NCN26000 maps link_ctrl to BMCR_ANENABLE
+#define NCN26000_BCMR_LINK_CTRL_BIT	BMCR_ANENABLE
+
+// the NCN26000 maps link_status to BMSR_ANEGCOMPLETE
+#define NCN26000_BMSR_LINK_STATUS_BIT	BMSR_ANEGCOMPLETE
+
+#define NCN26000_IRQ_LINKST_BIT		BIT(0)
+#define NCN26000_IRQ_PLCAST_BIT		BIT(1)
+#define NCN26000_IRQ_LJABBER_BIT	BIT(2)
+#define NCN26000_IRQ_RJABBER_BIT	BIT(3)
+#define NCN26000_IRQ_PLCAREC_BIT	BIT(4)
+#define NCN26000_IRQ_PHYSCOL_BIT	BIT(5)
+
+#define TO_TMR_DEFAULT			32
+
+struct ncn26000_priv {
+	u16 enabled_irqs;
+};
+
+// module parameter: if set, the link status is derived from the PLCA status
+// default: false
+static bool link_status_plca;
+module_param(link_status_plca, bool, 0644);
+
+// driver callbacks
+
+static int ncn26000_config_init(struct phy_device *phydev)
+{
+	/* HW bug workaround: the default value of the PLCA TO_TIMER should be
+	 * 32, where the current version of NCN26000 reports 24. This will be
+	 * fixed in future PHY versions. For the time being, we force the
+	 * correct default here.
+	 */
+	return phy_write_mmd(phydev, MDIO_MMD_OATC14, MDIO_OATC14_PLCA_TOTMR,
+			     TO_TMR_DEFAULT);
+}
+
+static int ncn26000_config_aneg(struct phy_device *phydev)
+{
+	// Note: the NCN26000 supports only P2MP link mode. Therefore, AN is not
+	// supported. However, this function is invoked by phylib to enable the
+	// PHY, regardless of the AN support.
+	phydev->mdix_ctrl = ETH_TP_MDI_AUTO;
+	phydev->mdix = ETH_TP_MDI;
+
+	// bring up the link
+	return phy_write(phydev, MII_BMCR, NCN26000_BCMR_LINK_CTRL_BIT);
+}
+
+static int ncn26000_get_features(struct phy_device *phydev)
+{
+	linkmode_zero(phydev->supported);
+	linkmode_set_bit(ETHTOOL_LINK_MODE_MII_BIT, phydev->supported);
+
+	linkmode_set_bit(ETHTOOL_LINK_MODE_10baseT1S_P2MP_Half_BIT,
+			 phydev->supported);
+
+	linkmode_copy(phydev->advertising, phydev->supported);
+	return 0;
+}
+
+static int ncn26000_read_status(struct phy_device *phydev)
+{
+	// The NCN26000 reports NCN26000_LINK_STATUS_BIT if the link status of
+	// the PHY is up. It further reports the logical AND of the link status
+	// and the PLCA status in the BMSR_LSTATUS bit. Thus, report the link
+	// status by testing the appropriate BMSR bit according to the module's
+	// parameter configuration.
+	const int lstatus_flag = link_status_plca ?
+		BMSR_LSTATUS : NCN26000_BMSR_LINK_STATUS_BIT;
+
+	int ret;
+
+	ret = phy_read(phydev, MII_BMSR);
+	if (unlikely(ret < 0))
+		return ret;
+
+	// update link status
+	phydev->link = (ret & lstatus_flag) ? 1 : 0;
+
+	// handle more IRQs here
+
+	return 0;
+}
+
+static irqreturn_t ncn26000_handle_interrupt(struct phy_device *phydev)
+{
+	const struct ncn26000_priv *const priv = phydev->priv;
+	int ret;
+
+	// clear the latched bits in MII_BMSR
+	phy_read(phydev, MII_BMSR);
+
+	// read and aknowledge the IRQ status register
+	ret = phy_read(phydev, NCN26000_REG_IRQ_STATUS);
+
+	if (unlikely(ret < 0) || (ret & priv->enabled_irqs) == 0)
+		return IRQ_NONE;
+
+	phy_trigger_machine(phydev);
+	return IRQ_HANDLED;
+}
+
+static int ncn26000_config_intr(struct phy_device *phydev)
+{
+	int ret;
+	struct ncn26000_priv *priv = phydev->priv;
+
+	if (phydev->interrupts == PHY_INTERRUPT_ENABLED) {
+		// acknowledge IRQs
+		ret = phy_read(phydev, NCN26000_REG_IRQ_STATUS);
+		if (ret < 0)
+			return ret;
+
+		// get link status notifications
+		priv->enabled_irqs = NCN26000_IRQ_LINKST_BIT;
+	} else {
+		// disable all IRQs
+		priv->enabled_irqs = 0;
+	}
+
+	ret = phy_write(phydev, NCN26000_REG_IRQ_CTL, priv->enabled_irqs);
+	if (ret != 0)
+		return ret;
+
+	return 0;
+}
+
+static int ncn26000_probe(struct phy_device *phydev)
+{
+	struct device *dev = &phydev->mdio.dev;
+	struct ncn26000_priv *priv;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	phydev->priv = priv;
+
+	return 0;
+}
+
+static struct phy_driver ncn26000_driver[] = {
+	{
+		PHY_ID_MATCH_MODEL(PHY_ID_NCN26000),
+		.name			= "NCN26000",
+		.probe                  = ncn26000_probe,
+		.get_features		= ncn26000_get_features,
+		.config_init            = ncn26000_config_init,
+		.config_intr            = ncn26000_config_intr,
+		.config_aneg		= ncn26000_config_aneg,
+		.read_status		= ncn26000_read_status,
+		.handle_interrupt       = ncn26000_handle_interrupt,
+		.get_plca_cfg		= genphy_c45_plca_get_cfg,
+		.set_plca_cfg		= genphy_c45_plca_set_cfg,
+		.get_plca_status	= genphy_c45_plca_get_status,
+		.soft_reset             = genphy_soft_reset,
+	},
+};
+
+module_phy_driver(ncn26000_driver);
+
+MODULE_DEVICE_TABLE(mdio, ncn26000_tbl);
+MODULE_AUTHOR("Piergiorgio Beruto");
+MODULE_DESCRIPTION("onsemi 10BASE-T1S PHY driver");
+MODULE_LICENSE("Dual BSD/GPL");