net: phy: add Broadcom BCM84881 PHY driver

Add a rudimentary Clause 45 driver for the BCM84881 PHY, found on
Methode DM7052 SFPs.

Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/phy/Kconfig

@@ -324,6 +324,12 @@ config BROADCOM_PHY
 	  Currently supports the BCM5411, BCM5421, BCM5461, BCM54616S, BCM5464,
 	  BCM5481, BCM54810 and BCM5482 PHYs.
 
+config BCM84881_PHY
+	bool "Broadcom BCM84881 PHY"
+	depends on PHYLIB=y
+	---help---
+	  Support the Broadcom BCM84881 PHY.
+
 config CICADA_PHY
 	tristate "Cicada PHYs"
 	---help---

drivers/net/phy/Makefile

@@ -62,6 +62,7 @@ obj-$(CONFIG_BCM87XX_PHY)	+= bcm87xx.o
 obj-$(CONFIG_BCM_CYGNUS_PHY)	+= bcm-cygnus.o
 obj-$(CONFIG_BCM_NET_PHYLIB)	+= bcm-phy-lib.o
 obj-$(CONFIG_BROADCOM_PHY)	+= broadcom.o
+obj-$(CONFIG_BCM84881_PHY)	+= bcm84881.o
 obj-$(CONFIG_CICADA_PHY)	+= cicada.o
 obj-$(CONFIG_CORTINA_PHY)	+= cortina.o
 obj-$(CONFIG_DAVICOM_PHY)	+= davicom.o

drivers/net/phy/bcm84881.c

@@ -0,0 +1,269 @@
+// SPDX-License-Identifier: GPL-2.0
+// Broadcom BCM84881 NBASE-T PHY driver, as found on a SFP+ module.
+// Copyright (C) 2019 Russell King, Deep Blue Solutions Ltd.
+//
+// Like the Marvell 88x3310, the Broadcom 84881 changes its host-side
+// interface according to the operating speed between 10GBASE-R,
+// 2500BASE-X and SGMII (but unlike the 88x3310, without the control
+// word).
+//
+// This driver only supports those aspects of the PHY that I'm able to
+// observe and test with the SFP+ module, which is an incomplete subset
+// of what this PHY is able to support. For example, I only assume it
+// supports a single lane Serdes connection, but it may be that the PHY
+// is able to support more than that.
+#include <linux/delay.h>
+#include <linux/module.h>
+#include <linux/phy.h>
+
+enum {
+	MDIO_AN_C22 = 0xffe0,
+};
+
+static int bcm84881_wait_init(struct phy_device *phydev)
+{
+	unsigned int tries = 20;
+	int ret, val;
+
+	do {
+		val = phy_read_mmd(phydev, MDIO_MMD_PMAPMD, MDIO_CTRL1);
+		if (val < 0) {
+			ret = val;
+			break;
+		}
+		if (!(val & MDIO_CTRL1_RESET)) {
+			ret = 0;
+			break;
+		}
+		if (!--tries) {
+			ret = -ETIMEDOUT;
+			break;
+		}
+		msleep(100);
+	} while (1);
+
+	if (ret)
+		phydev_err(phydev, "%s failed: %d\n", __func__, ret);
+
+	return ret;
+}
+
+static int bcm84881_config_init(struct phy_device *phydev)
+{
+	switch (phydev->interface) {
+	case PHY_INTERFACE_MODE_SGMII:
+	case PHY_INTERFACE_MODE_2500BASEX:
+	case PHY_INTERFACE_MODE_10GKR:
+		break;
+	default:
+		return -ENODEV;
+	}
+	return 0;
+}
+
+static int bcm84881_probe(struct phy_device *phydev)
+{
+	/* This driver requires PMAPMD and AN blocks */
+	const u32 mmd_mask = MDIO_DEVS_PMAPMD | MDIO_DEVS_AN;
+
+	if (!phydev->is_c45 ||
+	    (phydev->c45_ids.devices_in_package & mmd_mask) != mmd_mask)
+		return -ENODEV;
+
+	return 0;
+}
+
+static int bcm84881_get_features(struct phy_device *phydev)
+{
+	int ret;
+
+	ret = genphy_c45_pma_read_abilities(phydev);
+	if (ret)
+		return ret;
+
+	/* Although the PHY sets bit 1.11.8, it does not support 10M modes */
+	linkmode_clear_bit(ETHTOOL_LINK_MODE_10baseT_Half_BIT,
+			   phydev->supported);
+	linkmode_clear_bit(ETHTOOL_LINK_MODE_10baseT_Full_BIT,
+			   phydev->supported);
+
+	return 0;
+}
+
+static int bcm84881_config_aneg(struct phy_device *phydev)
+{
+	bool changed = false;
+	u32 adv;
+	int ret;
+
+	/* Wait for the PHY to finish initialising, otherwise our
+	 * advertisement may be overwritten.
+	 */
+	ret = bcm84881_wait_init(phydev);
+	if (ret)
+		return ret;
+
+	/* We don't support manual MDI control */
+	phydev->mdix_ctrl = ETH_TP_MDI_AUTO;
+
+	/* disabled autoneg doesn't seem to work with this PHY */
+	if (phydev->autoneg == AUTONEG_DISABLE)
+		return -EINVAL;
+
+	ret = genphy_c45_an_config_aneg(phydev);
+	if (ret < 0)
+		return ret;
+	if (ret > 0)
+		changed = true;
+
+	adv = linkmode_adv_to_mii_ctrl1000_t(phydev->advertising);
+	ret = phy_modify_mmd_changed(phydev, MDIO_MMD_AN,
+				     MDIO_AN_C22 + MII_CTRL1000,
+				     ADVERTISE_1000FULL | ADVERTISE_1000HALF,
+				     adv);
+	if (ret < 0)
+		return ret;
+	if (ret > 0)
+		changed = true;
+
+	return genphy_c45_check_and_restart_aneg(phydev, changed);
+}
+
+static int bcm84881_aneg_done(struct phy_device *phydev)
+{
+	int bmsr, val;
+
+	val = phy_read_mmd(phydev, MDIO_MMD_AN, MDIO_STAT1);
+	if (val < 0)
+		return val;
+
+	bmsr = phy_read_mmd(phydev, MDIO_MMD_AN, MDIO_AN_C22 + MII_BMSR);
+	if (bmsr < 0)
+		return val;
+
+	return !!(val & MDIO_AN_STAT1_COMPLETE) &&
+	       !!(bmsr & BMSR_ANEGCOMPLETE);
+}
+
+static int bcm84881_read_status(struct phy_device *phydev)
+{
+	unsigned int mode;
+	int bmsr, val;
+
+	val = phy_read_mmd(phydev, MDIO_MMD_AN, MDIO_CTRL1);
+	if (val < 0)
+		return val;
+
+	if (val & MDIO_AN_CTRL1_RESTART) {
+		phydev->link = 0;
+		return 0;
+	}
+
+	val = phy_read_mmd(phydev, MDIO_MMD_AN, MDIO_STAT1);
+	if (val < 0)
+		return val;
+
+	bmsr = phy_read_mmd(phydev, MDIO_MMD_AN, MDIO_AN_C22 + MII_BMSR);
+	if (bmsr < 0)
+		return val;
+
+	phydev->autoneg_complete = !!(val & MDIO_AN_STAT1_COMPLETE) &&
+				   !!(bmsr & BMSR_ANEGCOMPLETE);
+	phydev->link = !!(val & MDIO_STAT1_LSTATUS) &&
+		       !!(bmsr & BMSR_LSTATUS);
+	if (phydev->autoneg == AUTONEG_ENABLE && !phydev->autoneg_complete)
+		phydev->link = false;
+
+	if (!phydev->link)
+		return 0;
+
+	linkmode_zero(phydev->lp_advertising);
+	phydev->speed = SPEED_UNKNOWN;
+	phydev->duplex = DUPLEX_UNKNOWN;
+	phydev->pause = 0;
+	phydev->asym_pause = 0;
+	phydev->mdix = 0;
+
+	if (phydev->autoneg_complete) {
+		val = genphy_c45_read_lpa(phydev);
+		if (val < 0)
+			return val;
+
+		val = phy_read_mmd(phydev, MDIO_MMD_AN,
+				   MDIO_AN_C22 + MII_STAT1000);
+		if (val < 0)
+			return val;
+
+		mii_stat1000_mod_linkmode_lpa_t(phydev->lp_advertising, val);
+
+		if (phydev->autoneg == AUTONEG_ENABLE)
+			phy_resolve_aneg_linkmode(phydev);
+	}
+
+	if (phydev->autoneg == AUTONEG_DISABLE) {
+		/* disabled autoneg doesn't seem to work, so force the link
+		 * down.
+		 */
+		phydev->link = 0;
+		return 0;
+	}
+
+	/* Set the host link mode - we set the phy interface mode and
+	 * the speed according to this register so that downshift works.
+	 * We leave the duplex setting as per the resolution from the
+	 * above.
+	 */
+	val = phy_read_mmd(phydev, MDIO_MMD_VEND1, 0x4011);
+	mode = (val & 0x1e) >> 1;
+	if (mode == 1 || mode == 2)
+		phydev->interface = PHY_INTERFACE_MODE_SGMII;
+	else if (mode == 3)
+		phydev->interface = PHY_INTERFACE_MODE_10GKR;
+	else if (mode == 4)
+		phydev->interface = PHY_INTERFACE_MODE_2500BASEX;
+	switch (mode & 7) {
+	case 1:
+		phydev->speed = SPEED_100;
+		break;
+	case 2:
+		phydev->speed = SPEED_1000;
+		break;
+	case 3:
+		phydev->speed = SPEED_10000;
+		break;
+	case 4:
+		phydev->speed = SPEED_2500;
+		break;
+	case 5:
+		phydev->speed = SPEED_5000;
+		break;
+	}
+
+	return genphy_c45_read_mdix(phydev);
+}
+
+static struct phy_driver bcm84881_drivers[] = {
+	{
+		.phy_id		= 0xae025150,
+		.phy_id_mask	= 0xfffffff0,
+		.name		= "Broadcom BCM84881",
+		.config_init	= bcm84881_config_init,
+		.probe		= bcm84881_probe,
+		.get_features	= bcm84881_get_features,
+		.config_aneg	= bcm84881_config_aneg,
+		.aneg_done	= bcm84881_aneg_done,
+		.read_status	= bcm84881_read_status,
+	},
+};
+
+module_phy_driver(bcm84881_drivers);
+
+/* FIXME: module auto-loading for Clause 45 PHYs seems non-functional */
+static struct mdio_device_id __maybe_unused bcm84881_tbl[] = {
+	{ 0xae025150, 0xfffffff0 },
+	{ },
+};
+MODULE_AUTHOR("Russell King");
+MODULE_DESCRIPTION("Broadcom BCM84881 PHY driver");
+MODULE_DEVICE_TABLE(mdio, bcm84881_tbl);
+MODULE_LICENSE("GPL");