[RFC PATCH net-next 7/8] net: phy: mtip_backplane: add driver for MoreThanIP backplane AN/LT core

[Vladimir Oltean]

For each networking SerDes lane on certain Layerscape SoCs, there is a
block, based on an IP core from MoreThanIP, which optionally handles
IEEE 802.3 clause 73 and clause 72, i.e. backplane auto-negotiation and
link training.

The hardware integration between the SerDes lane and this AN/LT block is
rather weak. For this reason, there is no automatic link training
performed in hardware, but rather, software needs to implement a custom,
SerDes-specific link training algorithm and use the AN/LT registers to
communicate it with the link partner. This driver is an inapt attempt to
do just that.

Since the MTIP AN/LT block may be, in premise, integrated in non-NXP
SoCs as well, the networking PHY driver implementation is as generic as
possible.

Initial support is present only for the LX2160A SoC and the single-lane
link modes (10G, 25G). For this SoC, the register map of the IP block
was a bit mangled, and we don't have any PHY ID. I didn't want to invent
one, so this driver probes on a specific compatible string, plus the
secondary "ethernet-phy-ieee802.3-c45" which makes the PHY library
recognize it as a clause 45 PHY and not an mdio_device.

Signed-off-by: Vladimir Oltean <vladimir.oltean@xxxxxxx>
---
 drivers/net/phy/Kconfig          |    7 +
 drivers/net/phy/Makefile         |    1 +
 drivers/net/phy/mtip_backplane.c | 1735 ++++++++++++++++++++++++++++++
 3 files changed, 1743 insertions(+)
 create mode 100644 drivers/net/phy/mtip_backplane.c

diff --git a/drivers/net/phy/Kconfig b/drivers/net/phy/Kconfig
index 107880d13d21..536ce9f118c5 100644
--- a/drivers/net/phy/Kconfig
+++ b/drivers/net/phy/Kconfig
@@ -290,6 +290,13 @@ config MOTORCOMM_PHY
 	  Enables support for Motorcomm network PHYs.
 	  Currently supports YT85xx Gigabit Ethernet PHYs.
 
+config MTIP_BACKPLANE_PHY
+	tristate "MoreThanIP copper backplane PHYs"
+	help
+	  Enable support for the MoreThanIP copper backplane Auto-Negotiation
+	  and Link Training blocks, as implemented on the QorIQ and Layerscape
+	  SoCs.
+
 config NATIONAL_PHY
 	tristate "National Semiconductor PHYs"
 	help
diff --git a/drivers/net/phy/Makefile b/drivers/net/phy/Makefile
index c945ed9bd14b..06ef4b59e223 100644
--- a/drivers/net/phy/Makefile
+++ b/drivers/net/phy/Makefile
@@ -81,6 +81,7 @@ obj-$(CONFIG_MICROCHIP_T1_PHY)	+= microchip_t1.o
 obj-$(CONFIG_MICROCHIP_T1S_PHY) += microchip_t1s.o
 obj-$(CONFIG_MICROSEMI_PHY)	+= mscc/
 obj-$(CONFIG_MOTORCOMM_PHY)	+= motorcomm.o
+obj-$(CONFIG_MTIP_BACKPLANE_PHY) += mtip_backplane.o
 obj-$(CONFIG_NATIONAL_PHY)	+= national.o
 obj-$(CONFIG_NCN26000_PHY)	+= ncn26000.o
 obj-$(CONFIG_NXP_C45_TJA11XX_PHY)	+= nxp-c45-tja11xx.o
diff --git a/drivers/net/phy/mtip_backplane.c b/drivers/net/phy/mtip_backplane.c
new file mode 100644
index 000000000000..09eeaff653aa
--- /dev/null
+++ b/drivers/net/phy/mtip_backplane.c
@@ -0,0 +1,1735 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Driver for MoreThanIP copper backplane AN/LT (Auto-Negotiation and
+ * Link Training) core
+ *
+ * Copyright 2023 NXP
+ */
+
+#include <linux/kernel.h>
+#include <linux/mii.h>
+#include <linux/module.h>
+#include <linux/of_mdio.h>
+#include <linux/phy.h>
+#include <linux/phy/phy.h>
+#include <linux/clk.h>
+
+#define BP_ETH_STAT_ALWAYS_1		BIT(0)
+#define BP_ETH_STAT_1GKX		BIT(1)
+#define BP_ETH_STAT_10GKX4		BIT(2)
+#define BP_ETH_STAT_10GKR		BIT(3)
+#define BP_ETH_STAT_FC_FEC		BIT(4)
+#define BP_ETH_STAT_40GKR4		BIT(5)
+#define BP_ETH_STAT_40GCR4		BIT(6)
+#define BP_ETH_STAT_RS_FEC		BIT(7)
+#define BP_ETH_STAT_100GCR10		BIT(8)
+#define BP_ETH_STAT_100GKP4		BIT(9)
+#define BP_ETH_STAT_100GKR4		BIT(10)
+#define BP_ETH_STAT_100GCR4		BIT(11)
+#define BP_ETH_STAT_25GKRS		BIT(12)
+#define BP_ETH_STAT_25GKR		BIT(13)
+
+#define BP_ETH_STAT_PARALLEL_DETECT	(BP_ETH_STAT_ALWAYS_1 | \
+					 BP_ETH_STAT_1GKX | \
+					 BP_ETH_STAT_10GKX4)
+
+#define LT_CTRL_RESTART_TRAINING	BIT(0)
+#define LT_CTRL_TRAINING_ENABLE		BIT(1)
+
+#define LT_STAT_RX_STATUS		BIT(0)
+#define LT_STAT_FRAME_LOCK		BIT(1)
+#define LT_STAT_IN_PROGRESS		BIT(2)
+#define LT_STAT_FAIL			BIT(3)
+#define LT_STAT_SIGNAL_DETECT		BIT(15)
+
+#define LT_COM1_MASK			GENMASK(1, 0)
+#define LT_COZ_MASK			GENMASK(3, 2)
+#define LT_COP1_MASK			GENMASK(5, 4)
+#define LT_COM1(x)			((x) & LT_COM1_MASK)
+#define LT_COM1_X(x)			((x) & LT_COM1_MASK)
+#define LT_COZ(x)			(((x) << 2) & LT_COZ_MASK)
+#define LT_COZ_X(x)			(((x) & LT_COZ_MASK) >> 2)
+#define LT_COP1(x)			(((x) << 4) & LT_COP1_MASK)
+#define LT_COP1_X(x)			(((x) & LT_COP1_MASK) >> 4)
+
+#define LT_COEF_STAT_MASK		(LT_COM1_MASK | LT_COZ_MASK | LT_COP1_MASK)
+#define LT_COEF_STAT_ALL_NOT_UPDATED(x)	(((x) & LT_COEF_STAT_MASK) == 0)
+#define LT_COEF_STAT_ANY_UPDATED(x)	(((x) & LT_COEF_STAT_MASK) != 0)
+
+#define LT_COEF_UPD_MASK		(LT_COM1_MASK | LT_COZ_MASK | LT_COP1_MASK)
+#define LT_COEF_UPD_ALL_HOLD		(LT_COM1(COEF_UPD_HOLD) | \
+					LT_COZ(COEF_UPD_HOLD) | \
+					LT_COP1(COEF_UPD_HOLD))
+
+#define LT_COEF_UPD_ANYTHING(x)		((x) != 0)
+#define LT_COEF_UPD_NOTHING(x)		((x) == 0)
+
+#define LT_COEF_UPD_INIT		BIT(12)
+#define LT_COEF_UPD_PRESET		BIT(13)
+
+#define LT_COEF_STAT_RX_READY		BIT(15)
+
+#define C73_ADV_0(x)			(u16)((x) & GENMASK(15, 0))
+#define C73_ADV_1(x)			(u16)(((x) & GENMASK(31, 16)) >> 16)
+#define C73_ADV_2(x)			(u16)(((x) & GENMASK_ULL(47, 32)) >> 32)
+
+#define IRQPOLL_INTERVAL		(HZ / 4)
+
+#define MTIP_CDR_SLEEP_US		100
+#define MTIP_CDR_TIMEOUT_US		100000
+
+#define MTIP_LT_RESTART_SLEEP_US	10
+#define MTIP_LT_RESTART_TIMEOUT_US	100
+
+#define MTIP_FRAME_LOCK_SLEEP_US	10
+#define MTIP_FRAME_LOCK_TIMEOUT_US	100
+
+#define MTIP_RESET_SLEEP_US		100
+#define MTIP_RESET_TIMEOUT_US		100000
+
+#define MTIP_BP_ETH_STAT_SLEEP_US	10
+#define MTIP_BP_ETH_STAT_TIMEOUT_US	100
+
+#define MTIP_COEF_STAT_SLEEP_US		10
+#define MTIP_COEF_STAT_TIMEOUT_US	500000
+
+#define MTIP_AN_TIMEOUT_MS		10000
+
+enum mtip_an_reg {
+	AN_CTRL,
+	AN_STAT,
+	AN_ADV_0,
+	AN_ADV_1,
+	AN_ADV_2,
+	AN_LPA_0,
+	AN_LPA_1,
+	AN_LPA_2,
+	AN_MS_CNT,
+	AN_ADV_XNP_0,
+	AN_ADV_XNP_1,
+	AN_ADV_XNP_2,
+	AN_LPA_XNP_0,
+	AN_LPA_XNP_1,
+	AN_LPA_XNP_2,
+	AN_BP_ETH_STAT,
+};
+
+enum mtip_lt_reg {
+	LT_CTRL,
+	LT_STAT,
+	LT_LP_COEF,
+	LT_LP_STAT,
+	LT_LD_COEF,
+	LT_LD_STAT,
+	LT_TRAIN_PATTERN,
+	LT_RX_PATTERN,
+	LT_RX_PATTERN_ERR,
+	LT_RX_PATTERN_BEGIN,
+};
+
+struct mtip_irqpoll {
+	struct phy_device *phydev;
+	struct mutex lock;
+	struct delayed_work work;
+	u16 old_an_stat;
+	u16 old_pcs_stat;
+	bool link;
+	bool link_ack;
+	bool cdr_locked;
+};
+
+struct mtip_lt_work {
+	struct phy_device *phydev;
+	struct kthread_work work;
+};
+
+struct mtip_backplane {
+	struct phy *serdes;
+	struct mdio_device *pcs;
+	const u16 *an_regs;
+	const u16 *lt_regs;
+	int lt_mmd;
+	enum ethtool_link_mode_bit_indices link_mode;
+	bool link_mode_resolved;
+	unsigned long last_an_restart;
+	struct mtip_irqpoll irqpoll;
+	struct kthread_worker *local_tx_lt_worker;
+	struct kthread_worker *remote_tx_lt_worker;
+	/* Serialized by an_restart_lock */
+	bool an_restart_pending;
+	bool an_enabled;
+	/* Used for orderly shutdown of LT threads. Modified without any
+	 * locking. Set to true only by the irqpoll thread, set to false
+	 * by irqpoll and by the LT threads.
+	 */
+	bool lt_enabled;
+	bool local_tx_lt_done;
+	bool remote_tx_lt_done;
+	/* Serialize concurrent attempts from the local TX and remote TX
+	 * kthreads to finalize their side of the link training
+	 */
+	struct mutex lt_lock;
+	struct mutex an_restart_lock;
+};
+
+#define phydev_to_irqpoll(phydev)	\
+	(&((struct mtip_backplane *)(phydev)->priv)->irqpoll)
+
+/* Auto-Negotiation Control and Status Registers are on page 0: 0x0 */
+static const u16 mtip_lx2160a_an_regs[] = {
+	[AN_CTRL] = 0,
+	[AN_STAT] = 1,
+	[AN_ADV_0] = 2,
+	[AN_ADV_1] = 3,
+	[AN_ADV_2] = 4,
+	[AN_LPA_0] = 5,
+	[AN_LPA_1] = 6,
+	[AN_LPA_2] = 7,
+	[AN_MS_CNT] = 8,
+	[AN_ADV_XNP_0] = 9,
+	[AN_ADV_XNP_1] = 10,
+	[AN_ADV_XNP_2] = 11,
+	[AN_LPA_XNP_0] = 12,
+	[AN_LPA_XNP_1] = 13,
+	[AN_LPA_XNP_2] = 14,
+	[AN_BP_ETH_STAT] = 15,
+};
+
+/* Link Training Control and Status Registers are on page 1: 256 = 0x100 */
+static const u16 mtip_lx2160a_lt_regs[] = {
+	[LT_CTRL] = 0x100,
+	[LT_STAT] = 0x101,
+	[LT_LP_COEF] = 0x102,
+	[LT_LP_STAT] = 0x103,
+	[LT_LD_COEF] = 0x104,
+	[LT_LD_STAT] = 0x105,
+	[LT_TRAIN_PATTERN] = 0x108,
+	[LT_RX_PATTERN] = 0x109,
+	[LT_RX_PATTERN_ERR] =  0x10a,
+	[LT_RX_PATTERN_BEGIN] = 0x10b,
+};
+
+static const enum ethtool_link_mode_bit_indices mtip_backplane_link_modes[] = {
+	ETHTOOL_LINK_MODE_10000baseKR_Full_BIT,
+	ETHTOOL_LINK_MODE_25000baseKR_Full_BIT,
+};
+
+static const char *
+ethtool_link_mode_str(enum ethtool_link_mode_bit_indices link_mode)
+{
+	switch (link_mode) {
+	case ETHTOOL_LINK_MODE_1000baseKX_Full_BIT:
+		return "1000base-KX";
+	case ETHTOOL_LINK_MODE_10000baseKR_Full_BIT:
+		return "10Gbase-KR";
+	case ETHTOOL_LINK_MODE_40000baseKR4_Full_BIT:
+		return "40Gbase-KR4";
+	case ETHTOOL_LINK_MODE_25000baseKR_Full_BIT:
+		return "25Gbase-KR";
+	case ETHTOOL_LINK_MODE_100000baseKR4_Full_BIT:
+		return "100Gbase-KR4";
+	default:
+		return "unknown";
+	}
+}
+
+static bool
+link_mode_needs_training(enum ethtool_link_mode_bit_indices link_mode)
+{
+	if (link_mode == ETHTOOL_LINK_MODE_1000baseKX_Full_BIT)
+		return false;
+
+	return true;
+}
+
+static int mtip_read_an(struct phy_device *phydev, enum mtip_an_reg reg)
+{
+	struct mtip_backplane *priv = phydev->priv;
+
+	return phy_read_mmd(phydev, MDIO_MMD_AN, priv->an_regs[reg]);
+}
+
+static int mtip_write_an(struct phy_device *phydev, enum mtip_an_reg reg,
+			 u16 val)
+{
+	struct mtip_backplane *priv = phydev->priv;
+
+	return phy_write_mmd(phydev, MDIO_MMD_AN, priv->an_regs[reg], val);
+}
+
+static int mtip_modify_an(struct phy_device *phydev, enum mtip_an_reg reg,
+			  u16 mask, u16 set)
+{
+	struct mtip_backplane *priv = phydev->priv;
+
+	return phy_modify_mmd(phydev, MDIO_MMD_AN, priv->an_regs[reg],
+			      mask, set);
+}
+
+static int mtip_read_lt(struct phy_device *phydev, enum mtip_lt_reg reg)
+{
+	struct mtip_backplane *priv = phydev->priv;
+
+	return phy_read_mmd(phydev, priv->lt_mmd, priv->lt_regs[reg]);
+}
+
+static int mtip_write_lt(struct phy_device *phydev, enum mtip_lt_reg reg,
+			 u16 val)
+{
+	struct mtip_backplane *priv = phydev->priv;
+
+	return phy_write_mmd(phydev, priv->lt_mmd, priv->lt_regs[reg], val);
+}
+
+static int mtip_modify_lt(struct phy_device *phydev, enum mtip_lt_reg reg,
+			  u16 mask, u16 set)
+{
+	struct mtip_backplane *priv = phydev->priv;
+
+	return phy_modify_mmd(phydev, priv->lt_mmd, priv->lt_regs[reg],
+			      mask, set);
+}
+
+static int mtip_read_pcs(struct phy_device *phydev, int reg)
+{
+	struct mtip_backplane *priv = phydev->priv;
+	struct mdio_device *pcs = priv->pcs;
+
+	return mdiodev_c45_read(pcs, MDIO_MMD_PCS, reg);
+}
+
+static int mtip_modify_pcs(struct phy_device *phydev, int reg, u16 mask,
+			   u16 set)
+{
+	struct mtip_backplane *priv = phydev->priv;
+	struct mdio_device *pcs = priv->pcs;
+
+	return mdiodev_c45_modify(pcs, MDIO_MMD_PCS, reg, mask, set);
+}
+
+static int mtip_reset_an(struct phy_device *phydev)
+{
+	int err, val;
+
+	err = mtip_modify_an(phydev, AN_CTRL, MDIO_CTRL1_RESET,
+			     MDIO_CTRL1_RESET);
+	if (err < 0)
+		return err;
+
+	err = read_poll_timeout(mtip_read_an, val,
+				val < 0 || !(val & MDIO_CTRL1_RESET),
+				MTIP_RESET_SLEEP_US, MTIP_RESET_TIMEOUT_US,
+				false, phydev, AN_CTRL);
+
+	return (val < 0) ? val : err;
+}
+
+static int mtip_reset_pcs(struct phy_device *phydev)
+{
+	int err, val;
+
+	err = mtip_modify_pcs(phydev, MDIO_CTRL1, MDIO_CTRL1_RESET,
+			      MDIO_CTRL1_RESET);
+	if (err < 0)
+		return err;
+
+	err = read_poll_timeout(mtip_read_pcs, val,
+				val < 0 || !(val & MDIO_CTRL1_RESET),
+				MTIP_RESET_SLEEP_US, MTIP_RESET_TIMEOUT_US,
+				false, phydev, MDIO_CTRL1);
+
+	return (val < 0) ? val : err;
+}
+
+static int mtip_wait_for_cdr_lock(struct phy_device *phydev)
+{
+	struct mtip_backplane *priv = phydev->priv;
+	bool cdr_locked;
+	int err, val;
+
+	err = read_poll_timeout(phy_check_cdr_lock, val,
+				val < 0 || cdr_locked,
+				MTIP_CDR_SLEEP_US, MTIP_CDR_TIMEOUT_US,
+				false, priv->serdes, &cdr_locked);
+
+	return (val < 0) ? val : err;
+}
+
+static int mtip_lx2160a_get_features(struct phy_device *phydev)
+{
+	const enum ethtool_link_mode_bit_indices *link_modes;
+	struct mtip_backplane *priv = phydev->priv;
+	int i, err;
+
+	linkmode_set_bit(ETHTOOL_LINK_MODE_Autoneg_BIT, phydev->supported);
+	linkmode_set_bit(ETHTOOL_LINK_MODE_Backplane_BIT, phydev->supported);
+	linkmode_set_bit(ETHTOOL_LINK_MODE_Pause_BIT, phydev->supported);
+	linkmode_set_bit(ETHTOOL_LINK_MODE_Asym_Pause_BIT, phydev->supported);
+
+	link_modes = mtip_backplane_link_modes;
+
+	/* Ask the SerDes driver what link modes are supported,
+	 * based on the current PLL configuration.
+	 */
+	for (i = 0; i < ARRAY_SIZE(mtip_backplane_link_modes); i++) {
+		err = phy_validate(priv->serdes, PHY_MODE_ETHERNET_PHY,
+				   link_modes[i], NULL);
+		if (err)
+			continue;
+
+		linkmode_set_bit(link_modes[i], phydev->supported);
+	}
+
+	return 0;
+}
+
+static int mtip_lt_frame_lock(struct phy_device *phydev)
+{
+	int err, val;
+
+	err = read_poll_timeout(mtip_read_lt, val,
+				val < 0 || (val & LT_STAT_FRAME_LOCK),
+				MTIP_FRAME_LOCK_SLEEP_US, MTIP_FRAME_LOCK_TIMEOUT_US,
+				false, phydev, LT_CTRL);
+
+	return (val < 0) ? val : err;
+}
+
+static int mtip_restart_lt(struct phy_device *phydev, bool enable)
+{
+	u16 mask = LT_CTRL_RESTART_TRAINING | LT_CTRL_TRAINING_ENABLE;
+	u16 set = LT_CTRL_RESTART_TRAINING;
+	int err, val;
+
+	if (enable)
+		set |= LT_CTRL_TRAINING_ENABLE;
+
+	err = mtip_modify_lt(phydev, LT_CTRL, mask, set);
+	if (err < 0)
+		return err;
+
+	err = read_poll_timeout(mtip_read_lt, val,
+				val < 0 || !(val & LT_CTRL_RESTART_TRAINING),
+				MTIP_LT_RESTART_SLEEP_US, MTIP_LT_RESTART_TIMEOUT_US,
+				false, phydev, LT_CTRL);
+
+	return (val < 0) ? val : err;
+}
+
+/* Enable the lane datapath by disconnecting it from the AN/LT block
+ * and connecting it to the PCS. This is called both from the irqpoll thread,
+ * as well as from the last link training kthread to finish.
+ */
+static int mtip_finish_lt(struct phy_device *phydev)
+{
+	struct mtip_backplane *priv = phydev->priv;
+	int err;
+
+	err = mtip_restart_lt(phydev, false);
+	if (err) {
+		phydev_err(phydev, "Failed to disable link training: %pe\n",
+			   ERR_PTR(err));
+		return err;
+	}
+
+	/* Subsequent attempts to disable LT will time out, so stop them */
+	WRITE_ONCE(priv->lt_enabled, false);
+
+	return 0;
+}
+
+static int mtip_stop_lt(struct phy_device *phydev)
+{
+	struct mtip_irqpoll *irqpoll = phydev_to_irqpoll(phydev);
+	struct mtip_backplane *priv = phydev->priv;
+	int err;
+
+	lockdep_assert_held(&irqpoll->lock);
+
+	kthread_flush_worker(priv->remote_tx_lt_worker);
+	kthread_flush_worker(priv->local_tx_lt_worker);
+
+	err = mtip_finish_lt(phydev);
+	if (err)
+		return err;
+
+	phydev_dbg(phydev, "Link training disabled\n");
+
+	return 0;
+}
+
+static int mtip_reset_lt(struct phy_device *phydev)
+{
+	int err;
+
+	/* Don't allow AN to complete without training */
+	err = mtip_modify_lt(phydev, LT_STAT, LT_STAT_RX_STATUS, 0);
+	if (err < 0)
+		return err;
+
+	err = mtip_write_lt(phydev, LT_LD_COEF, 0);
+	if (err < 0)
+		return err;
+
+	err = mtip_write_lt(phydev, LT_LD_STAT, 0);
+	if (err < 0)
+		return err;
+
+	return 0;
+}
+
+/* Reset state when detecting that the previously determined link mode
+ * is no longer valid
+ */
+static int mtip_state_reset(struct phy_device *phydev)
+{
+	struct mtip_backplane *priv = phydev->priv;
+	int err;
+
+	priv->link_mode_resolved = false;
+
+	if (READ_ONCE(priv->lt_enabled)) {
+		err = mtip_stop_lt(phydev);
+		if (err)
+			return err;
+	}
+
+	err = mtip_reset_lt(phydev);
+	if (err < 0)
+		return err;
+
+	return 0;
+}
+
+/* Make sure we don't act on old event bits from previous runs when
+ * we restart autoneg.
+ */
+static int mtip_unlatch_an_stat(struct phy_device *phydev)
+{
+	struct mtip_irqpoll *irqpoll = phydev_to_irqpoll(phydev);
+	int val;
+
+	lockdep_assert_held(&irqpoll->lock);
+
+	val = mtip_read_an(phydev, AN_STAT);
+	if (val < 0)
+		return val;
+
+	/* Discard the current AN status, it will become invalid soon */
+	irqpoll->old_an_stat = 0;
+
+	return 0;
+}
+
+/* Suppress a "PCS link dropped, restarting autoneg" event when initiating
+ * an autoneg restart locally.
+ */
+static int mtip_unlatch_pcs_stat(struct phy_device *phydev)
+{
+	struct mtip_irqpoll *irqpoll = phydev_to_irqpoll(phydev);
+
+	irqpoll->old_pcs_stat = 0;
+
+	return 0;
+}
+
+static int mtip_read_adv(struct phy_device *phydev, u64 *base_page)
+{
+	int val;
+
+	val = mtip_read_an(phydev, AN_ADV_0);
+	if (val < 0)
+		return val;
+
+	*base_page = (u64)val;
+
+	val = mtip_read_an(phydev, AN_ADV_1);
+	if (val < 0)
+		return val;
+
+	*base_page |= (u64)val << 16;
+
+	val = mtip_read_an(phydev, AN_ADV_2);
+	if (val < 0)
+		return val;
+
+	*base_page |= (u64)val << 32;
+
+	return 0;
+}
+
+static int mtip_write_adv(struct phy_device *phydev, u64 base_page)
+{
+	int val;
+
+	val = mtip_write_an(phydev, AN_ADV_0, C73_ADV_0(base_page));
+	if (val < 0)
+		return val;
+
+	val = mtip_write_an(phydev, AN_ADV_1, C73_ADV_1(base_page));
+	if (val < 0)
+		return val;
+
+	val = mtip_write_an(phydev, AN_ADV_2, C73_ADV_2(base_page));
+	if (val < 0)
+		return val;
+
+	return 0;
+}
+
+static int mtip_read_lpa(struct phy_device *phydev, u64 *base_page)
+{
+	int val;
+
+	val = mtip_read_an(phydev, AN_LPA_0);
+	if (val < 0)
+		return val;
+
+	*base_page = (u64)val;
+
+	val = mtip_read_an(phydev, AN_LPA_1);
+	if (val < 0)
+		return val;
+
+	*base_page |= (u64)val << 16;
+
+	val = mtip_read_an(phydev, AN_LPA_2);
+	if (val < 0)
+		return val;
+
+	*base_page |= (u64)val << 32;
+
+	return 0;
+}
+
+static int mtip_config_an_adv(struct phy_device *phydev)
+{
+	u64 base_page = linkmode_adv_to_c73_base_page(phydev->advertising);
+	u8 nonce;
+
+	/* The transmitted nonce must not be equal with the one transmitted by
+	 * the link partner, otherwise AN will not complete (nonce_match=true).
+	 * With purely randomly generated nonces, that is always a chance
+	 * though. 98.2.1.2.3 Transmitted Nonce Field gives a way for
+	 * management to avoid that.
+	 */
+	get_random_bytes(&nonce, sizeof(nonce));
+
+	switch (phydev->master_slave_set) {
+	case MASTER_SLAVE_CFG_MASTER_PREFERRED:
+	case MASTER_SLAVE_CFG_MASTER_FORCE:
+		nonce |= BIT(4);
+		break;
+	case MASTER_SLAVE_CFG_SLAVE_PREFERRED:
+	case MASTER_SLAVE_CFG_SLAVE_FORCE:
+		nonce &= ~BIT(4);
+		break;
+	}
+
+	base_page |= C73_BASE_PAGE_TRANSMITTED_NONCE(nonce);
+	/* According to Annex 28A, set Selector to "IEEE 802.3" */
+	base_page |= C73_BASE_PAGE_SELECTOR(1);
+	/* C73_BASE_PAGE_ACK and C73_BASE_PAGE_ECHOED_NONCE seem to have
+	 * a life of their own, regardless of what we set them to.
+	 */
+
+	return mtip_write_adv(phydev, base_page);
+}
+
+static int mtip_an_restart(struct phy_device *phydev)
+{
+	struct mtip_backplane *priv = phydev->priv;
+	int err;
+
+	err = mtip_state_reset(phydev);
+	if (err)
+		return err;
+
+	/* Make sure AN is temporarily disabled, so that we can safely
+	 * unlatch the previous status without losing real events
+	 */
+	err = mtip_reset_an(phydev);
+	if (err < 0)
+		return err;
+
+	err = mtip_unlatch_an_stat(phydev);
+	if (err)
+		return err;
+
+	err = mtip_unlatch_pcs_stat(phydev);
+	if (err)
+		return err;
+
+	err = mtip_config_an_adv(phydev);
+	if (err < 0)
+		return err;
+
+	err = mtip_modify_an(phydev, AN_CTRL,
+			     MDIO_AN_CTRL1_ENABLE | MDIO_AN_CTRL1_RESTART,
+			     MDIO_AN_CTRL1_ENABLE | MDIO_AN_CTRL1_RESTART);
+	if (err < 0)
+		return err;
+
+	priv->last_an_restart = jiffies;
+	priv->an_restart_pending = false;
+
+	return 0;
+}
+
+/* The reason for deferral is that the irqpoll thread waits for the LT kthreads
+ * to finish with irqpoll->lock held, and AN restart also requires holding the
+ * irqpoll->lock. So the kthreads cannot directly restart autoneg without
+ * deadlocking with the irqpoll thread, they must signal to the irqpoll thread
+ * to do so.
+ */
+static void mtip_an_restart_from_lt(struct phy_device *phydev)
+{
+	struct mtip_backplane *priv = phydev->priv;
+
+	mutex_lock(&priv->an_restart_lock);
+	priv->an_restart_pending = true;
+	mutex_unlock(&priv->an_restart_lock);
+}
+
+static int mtip_finalize_lt(struct phy_device *phydev)
+{
+	struct mtip_backplane *priv = phydev->priv;
+	union phy_configure_opts opts = {
+		.xgkr = {
+			.type = XGKR_CONFIGURE_LT_DONE,
+		},
+	};
+	int err, val;
+
+	lockdep_assert_held(&priv->lt_lock);
+
+	if (!priv->local_tx_lt_done || !priv->remote_tx_lt_done)
+		return 0;
+
+	/* Let the local state machine know we're done */
+	err = mtip_modify_lt(phydev, LT_STAT, LT_STAT_RX_STATUS,
+			     LT_STAT_RX_STATUS);
+	if (err < 0) {
+		phydev_err(phydev, "Failed to update LT_STAT: %pe\n",
+			   ERR_PTR(err));
+		return err;
+	}
+
+	err = mtip_finish_lt(phydev);
+	if (err)
+		return err;
+
+	val = mtip_read_lt(phydev, LT_STAT);
+	if (val < 0)
+		return val;
+
+	if (!(val & LT_STAT_SIGNAL_DETECT) || (val & LT_STAT_FAIL)) {
+		phydev_err(phydev,
+			   "Link training did not succeed: LT_STAT = 0x%x\n",
+			   val);
+		return -ENETDOWN;
+	}
+
+	return phy_configure(priv->serdes, &opts);
+}
+
+static int mtip_tx_c72_coef_update(struct phy_device *phydev,
+				   const struct c72_coef_update *upd,
+				   struct c72_coef_status *stat)
+{
+	char upd_buf[C72_COEF_UPDATE_BUFSIZ], stat_buf[C72_COEF_STATUS_BUFSIZ];
+	int err, val;
+	u16 ld_coef;
+
+	c72_coef_update_print(upd, upd_buf);
+
+	err = read_poll_timeout(mtip_read_lt, val,
+				val < 0 || LT_COEF_STAT_ALL_NOT_UPDATED(val),
+				MTIP_COEF_STAT_SLEEP_US, MTIP_COEF_STAT_TIMEOUT_US,
+				false, phydev, LT_LP_STAT);
+	if (val < 0)
+		return val;
+	if (err) {
+		phydev_err(phydev,
+			   "LP did not set coefficient status to NOT_UPDATED, couldn't send %s; LP_STAT = 0x%x\n",
+			   upd_buf, val);
+		return err;
+	}
+
+	ld_coef = LT_COM1(upd->com1) | LT_COZ(upd->coz) | LT_COP1(upd->cop1);
+	if (upd->init)
+		ld_coef |= LT_COEF_UPD_INIT;
+	if (upd->preset)
+		ld_coef |= LT_COEF_UPD_PRESET;
+
+	err = mtip_write_lt(phydev, LT_LD_COEF, ld_coef);
+	if (err < 0)
+		return err;
+
+	err = read_poll_timeout(mtip_read_lt, val,
+				val < 0 || LT_COEF_STAT_ANY_UPDATED(val),
+				MTIP_COEF_STAT_SLEEP_US, MTIP_COEF_STAT_TIMEOUT_US,
+				false, phydev, LT_LP_STAT);
+	if (val < 0)
+		return val;
+	if (err) {
+		phydev_err(phydev,
+			   "LP did not update coefficient status for %s; LP_STAT = 0x%x\n",
+			   upd_buf, val);
+		return err;
+	}
+
+	stat->com1 = LT_COM1_X(val);
+	stat->coz = LT_COZ_X(val);
+	stat->cop1 = LT_COP1_X(val);
+	c72_coef_status_print(stat, stat_buf);
+
+	ld_coef = LT_COM1(COEF_UPD_HOLD) | LT_COZ(COEF_UPD_HOLD) |
+		  LT_COP1(COEF_UPD_HOLD);
+	err = mtip_write_lt(phydev, LT_LD_COEF, ld_coef);
+	if (err < 0)
+		return err;
+
+	phydev_dbg(phydev, "Sent update: %s, got status: %s\n",
+		   upd_buf, stat_buf);
+
+	return 0;
+}
+
+static int mtip_c72_process_request(struct phy_device *phydev,
+				    const struct c72_coef_update *upd,
+				    struct c72_coef_status *stat)
+{
+	struct mtip_backplane *priv = phydev->priv;
+	union phy_configure_opts opts = {
+		.xgkr = {
+			.type = XGKR_CONFIGURE_LOCAL_TX,
+			.local_tx = {
+				.update = *upd,
+			},
+		},
+	};
+	int err;
+
+	err = phy_configure(priv->serdes, &opts);
+	if (err)
+		return err;
+
+	*stat = opts.xgkr.local_tx.status;
+
+	return 0;
+}
+
+static int mtip_read_lt_lp_coef_if_not_ready(struct phy_device *phydev,
+					     bool *rx_ready)
+{
+	int val;
+
+	val = mtip_read_lt(phydev, LT_LP_STAT);
+	if (val < 0)
+		return val;
+
+	*rx_ready = !!(val & LT_COEF_STAT_RX_READY);
+	if (*rx_ready)
+		return 0;
+
+	return mtip_read_lt(phydev, LT_LP_COEF);
+}
+
+static int mtip_rx_c72_coef_update(struct phy_device *phydev,
+				   struct c72_coef_update *upd,
+				   bool *rx_ready)
+{
+	char upd_buf[C72_COEF_UPDATE_BUFSIZ], stat_buf[C72_COEF_STATUS_BUFSIZ];
+	struct c72_coef_status stat = {};
+	int err, val;
+
+	err = read_poll_timeout(mtip_read_lt_lp_coef_if_not_ready,
+				val, val < 0 || *rx_ready || LT_COEF_UPD_ANYTHING(val),
+				MTIP_COEF_STAT_SLEEP_US, MTIP_COEF_STAT_TIMEOUT_US,
+				false, phydev, rx_ready);
+	if (val < 0)
+		return val;
+	if (*rx_ready) {
+		phydev_dbg(phydev, "LP says its RX is ready\n");
+		return 0;
+	}
+	if (err) {
+		phydev_err(phydev,
+			   "LP did not request coefficient updates; LP_COEF = 0x%x\n",
+			   val);
+		return err;
+	}
+
+	upd->com1 = LT_COM1_X(val);
+	upd->coz = LT_COZ_X(val);
+	upd->cop1 = LT_COP1_X(val);
+	upd->init = !!(val & LT_COEF_UPD_INIT);
+	upd->preset = !!(val & LT_COEF_UPD_PRESET);
+	c72_coef_update_print(upd, upd_buf);
+
+	if ((upd->com1 || upd->coz || upd->cop1) + upd->init + upd->preset > 1) {
+		phydev_warn(phydev, "Ignoring illegal request: %s (LP_COEF = 0x%x)\n",
+			    upd_buf, val);
+		return 0;
+	}
+
+	err = mtip_c72_process_request(phydev, upd, &stat);
+	if (err)
+		return err;
+
+	c72_coef_status_print(&stat, stat_buf);
+	phydev_dbg(phydev, "Received update: %s, responded with status: %s\n",
+		   upd_buf, stat_buf);
+
+	err = mtip_modify_lt(phydev, LT_LD_STAT, LT_COEF_STAT_MASK,
+			     LT_COM1(stat.com1) | LT_COZ(stat.coz) |
+			     LT_COP1(stat.cop1));
+	if (err < 0)
+		return err;
+
+	err = read_poll_timeout(mtip_read_lt, val,
+				val < 0 || LT_COEF_UPD_NOTHING(val),
+				MTIP_COEF_STAT_SLEEP_US, MTIP_COEF_STAT_TIMEOUT_US,
+				false, phydev, LT_LP_COEF);
+	if (val < 0)
+		return val;
+	if (err) {
+		phydev_err(phydev, "LP did not revert to HOLD; LP_COEF = 0x%x\n",
+			   val);
+		return err;
+	}
+
+	err = mtip_modify_lt(phydev, LT_LD_STAT, LT_COEF_STAT_MASK,
+			     LT_COM1(COEF_STAT_NOT_UPDATED) |
+			     LT_COZ(COEF_STAT_NOT_UPDATED) |
+			     LT_COP1(COEF_STAT_NOT_UPDATED));
+	if (err < 0)
+		return err;
+
+	return 0;
+}
+
+static int mtip_local_tx_lt_done(struct phy_device *phydev)
+{
+	struct mtip_backplane *priv = phydev->priv;
+	int err;
+
+	mutex_lock(&priv->lt_lock);
+
+	priv->local_tx_lt_done = true;
+
+	err = mtip_finalize_lt(phydev);
+
+	mutex_unlock(&priv->lt_lock);
+
+	return err;
+}
+
+static int mtip_remote_tx_lt_done(struct phy_device *phydev)
+{
+	struct mtip_backplane *priv = phydev->priv;
+	int err;
+
+	mutex_lock(&priv->lt_lock);
+
+	priv->remote_tx_lt_done = true;
+
+	err = mtip_finalize_lt(phydev);
+
+	mutex_unlock(&priv->lt_lock);
+
+	return err;
+}
+
+/* This is our hardware-based 500 ms timer for the link training */
+static bool mtip_lt_in_progress(struct phy_device *phydev)
+{
+	int val;
+
+	val = mtip_read_lt(phydev, LT_STAT);
+	if (val < 0)
+		return false;
+
+	return !!(val & LT_STAT_IN_PROGRESS);
+}
+
+/* Make adjustments to the local TX according to link partner requests,
+ * so that its RX improves
+ */
+static void mtip_local_tx_lt_work(struct kthread_work *work)
+{
+	struct mtip_lt_work *lt_work = container_of(work, struct mtip_lt_work,
+						    work);
+	struct phy_device *phydev = lt_work->phydev;
+	struct mtip_backplane *priv = phydev->priv;
+	int err;
+
+	err = mtip_lt_frame_lock(phydev);
+	if (err) {
+		phydev_err(phydev,
+			   "Failed to acquire training frame delineation: %pe\n",
+			   ERR_PTR(err));
+		goto out;
+	}
+
+	while (READ_ONCE(priv->lt_enabled)) {
+		struct c72_coef_update upd = {};
+		bool rx_ready;
+
+		if (!mtip_lt_in_progress(phydev)) {
+			phydev_err(phydev, "Local TX LT timed out\n");
+			break;
+		}
+
+		err = mtip_rx_c72_coef_update(phydev, &upd, &rx_ready);
+		if (err)
+			goto out;
+
+		if (rx_ready) {
+			err = mtip_local_tx_lt_done(phydev);
+			if (err) {
+				phydev_err(phydev, "Failed to finalize local LT: %pe\n",
+					   ERR_PTR(err));
+				goto out;
+			}
+			break;
+		}
+	}
+
+out:
+	if (err && READ_ONCE(priv->lt_enabled))
+		mtip_an_restart_from_lt(phydev);
+
+	kfree(lt_work);
+}
+
+/* Train the link partner TX, so that the local RX quality improves */
+static void mtip_remote_tx_lt_work(struct kthread_work *work)
+{
+	struct mtip_lt_work *lt_work = container_of(work, struct mtip_lt_work,
+						    work);
+	struct phy_device *phydev = lt_work->phydev;
+	struct mtip_backplane *priv = phydev->priv;
+	int err;
+
+	err = mtip_lt_frame_lock(phydev);
+	if (err) {
+		phydev_err(phydev,
+			   "Failed to acquire training frame delineation: %pe\n",
+			   ERR_PTR(err));
+		goto out;
+	}
+
+	while (true) {
+		struct c72_coef_status status = {};
+		union phy_configure_opts opts = {
+			.xgkr = {
+				.type = XGKR_CONFIGURE_REMOTE_TX,
+			},
+		};
+
+		if (!READ_ONCE(priv->lt_enabled))
+			goto out;
+
+		if (!mtip_lt_in_progress(phydev)) {
+			phydev_err(phydev, "Remote TX LT timed out\n");
+			goto out;
+		}
+
+		err = phy_configure(priv->serdes, &opts);
+		if (err) {
+			phydev_err(phydev,
+				   "Failed to get remote TX training request from SerDes: %pe\n",
+				   ERR_PTR(err));
+			goto out;
+		}
+
+		if (opts.xgkr.remote_tx.rx_ready)
+			break;
+
+		err = mtip_tx_c72_coef_update(phydev, &opts.xgkr.remote_tx.update,
+					      &status);
+		if (opts.xgkr.remote_tx.cb)
+			opts.xgkr.remote_tx.cb(opts.xgkr.remote_tx.cb_priv, err,
+					       opts.xgkr.remote_tx.update,
+					       status);
+		if (err)
+			goto out;
+	}
+
+	/* Let the link partner know we're done */
+	err = mtip_modify_lt(phydev, LT_LD_STAT, LT_COEF_STAT_RX_READY,
+			     LT_COEF_STAT_RX_READY);
+	if (err < 0) {
+		phydev_err(phydev, "Failed to update LT_LD_STAT: %pe\n",
+			   ERR_PTR(err));
+		goto out;
+	}
+
+	err = mtip_remote_tx_lt_done(phydev);
+	if (err) {
+		phydev_err(phydev, "Failed to finalize remote LT: %pe\n",
+			   ERR_PTR(err));
+		goto out;
+	}
+
+out:
+	if (err && READ_ONCE(priv->lt_enabled))
+		mtip_an_restart_from_lt(phydev);
+
+	kfree(lt_work);
+}
+
+static int mtip_start_lt(struct phy_device *phydev)
+{
+	struct mtip_irqpoll *irqpoll = phydev_to_irqpoll(phydev);
+	struct mtip_backplane *priv = phydev->priv;
+	struct mtip_lt_work *remote_tx_lt_work;
+	struct mtip_lt_work *local_tx_lt_work;
+	int err;
+
+	lockdep_assert_held(&irqpoll->lock);
+
+	local_tx_lt_work = kzalloc(sizeof(*local_tx_lt_work), GFP_KERNEL);
+	if (!local_tx_lt_work) {
+		err = -ENOMEM;
+		goto out;
+	}
+
+	remote_tx_lt_work = kzalloc(sizeof(*remote_tx_lt_work), GFP_KERNEL);
+	if (!remote_tx_lt_work) {
+		err = -ENOMEM;
+		goto out_free_local_tx_lt;
+	}
+
+	err = mtip_reset_lt(phydev);
+	if (err)
+		goto out_free_remote_tx_lt;
+
+	err = mtip_restart_lt(phydev, true);
+	if (err)
+		goto out_free_remote_tx_lt;
+
+	priv->local_tx_lt_done = false;
+	priv->remote_tx_lt_done = false;
+	WRITE_ONCE(priv->lt_enabled, true);
+
+	local_tx_lt_work->phydev = phydev;
+	kthread_init_work(&local_tx_lt_work->work, mtip_local_tx_lt_work);
+	kthread_queue_work(priv->local_tx_lt_worker, &local_tx_lt_work->work);
+
+	remote_tx_lt_work->phydev = phydev;
+	kthread_init_work(&remote_tx_lt_work->work, mtip_remote_tx_lt_work);
+	kthread_queue_work(priv->remote_tx_lt_worker, &remote_tx_lt_work->work);
+
+	phydev_dbg(phydev, "Link training enabled\n");
+
+	return 0;
+
+out_free_remote_tx_lt:
+	kfree(remote_tx_lt_work);
+out_free_local_tx_lt:
+	kfree(local_tx_lt_work);
+out:
+	return err;
+}
+
+static void mtip_update_link_latch(struct phy_device *phydev,
+				   bool cdr_locked, bool phy_los,
+				   bool an_complete, bool pcs_lstat)
+{
+	struct mtip_irqpoll *irqpoll = phydev_to_irqpoll(phydev);
+	struct mtip_backplane *priv = phydev->priv;
+
+	lockdep_assert_held(&irqpoll->lock);
+
+	/* Update irqpoll->link if true, or if false
+	 * and mtip_read_status() saw that already.
+	 */
+	if (irqpoll->link || irqpoll->link_ack) {
+		irqpoll->link = phy_los && cdr_locked && an_complete && pcs_lstat;
+		irqpoll->link_ack = false;
+	}
+
+	phydev_dbg(phydev, "PCS link%s: %d, PHY LOS: %d, CDR locked: %d, AN complete: %d\n",
+		   priv->link_mode_resolved ? "" : " (ignored)",
+		   pcs_lstat, phy_los, cdr_locked, an_complete);
+}
+
+static bool mtip_cached_an_complete(struct phy_device *phydev)
+{
+	struct mtip_irqpoll *irqpoll = phydev_to_irqpoll(phydev);
+
+	lockdep_assert_held(&irqpoll->lock);
+
+	return !!(irqpoll->old_an_stat & MDIO_AN_STAT1_COMPLETE);
+}
+
+static bool mtip_read_link_unlatch(struct phy_device *phydev)
+{
+	struct mtip_irqpoll *irqpoll = phydev_to_irqpoll(phydev);
+	bool old_link = irqpoll->link;
+
+	lockdep_assert_held(&irqpoll->lock);
+
+	/* A change to the link status may have occurred while a link
+	 * loss was latched, so update it again after reading it
+	 */
+	irqpoll->link = !!(irqpoll->old_an_stat & MDIO_STAT1_LSTATUS) &&
+			!!(irqpoll->old_an_stat & MDIO_AN_STAT1_COMPLETE) &&
+			!!(irqpoll->old_pcs_stat & MDIO_STAT1_LSTATUS) &&
+			irqpoll->cdr_locked;
+	irqpoll->link_ack = true;
+
+	return old_link;
+}
+
+static u16 mtip_expected_bp_eth_stat(enum ethtool_link_mode_bit_indices link_mode)
+{
+	switch (link_mode) {
+	case ETHTOOL_LINK_MODE_1000baseKX_Full_BIT:
+		return BP_ETH_STAT_ALWAYS_1 | BP_ETH_STAT_1GKX;
+	case ETHTOOL_LINK_MODE_10000baseKR_Full_BIT:
+		return BP_ETH_STAT_ALWAYS_1 | BP_ETH_STAT_10GKR;
+	case ETHTOOL_LINK_MODE_40000baseKR4_Full_BIT:
+		return BP_ETH_STAT_ALWAYS_1 | BP_ETH_STAT_40GKR4;
+	case ETHTOOL_LINK_MODE_25000baseKR_Full_BIT:
+		return BP_ETH_STAT_ALWAYS_1 | BP_ETH_STAT_25GKR;
+	case ETHTOOL_LINK_MODE_100000baseKR4_Full_BIT:
+		return BP_ETH_STAT_ALWAYS_1 | BP_ETH_STAT_100GKR4;
+	default:
+		return 0;
+	}
+}
+
+static int mtip_wait_bp_eth_stat(struct phy_device *phydev,
+				 enum ethtool_link_mode_bit_indices link_mode)
+{
+	u16 expected = mtip_expected_bp_eth_stat(link_mode);
+	int err, val;
+
+	err = read_poll_timeout(mtip_read_an, val,
+				val < 0 || val == expected,
+				MTIP_BP_ETH_STAT_SLEEP_US,
+				MTIP_BP_ETH_STAT_TIMEOUT_US,
+				false, phydev, AN_BP_ETH_STAT);
+	if (val < 0)
+		return val;
+
+	if (err) {
+		phydev_warn(phydev,
+			    "BP_ETH_STAT did not become 0x%x to indicate resolved link mode %s, instead it shows 0x%x%s\n",
+			    expected, ethtool_link_mode_str(link_mode), val,
+			    val == BP_ETH_STAT_PARALLEL_DETECT ? " (parallel detection)" : "");
+		/* It seems less consequential to ignore the error
+		 * than to restart autoneg...
+		 */
+	}
+
+	return 0;
+}
+
+static int mtip_c73_page_received(struct phy_device *phydev, bool *restart_an)
+{
+	__ETHTOOL_DECLARE_LINK_MODE_MASK(lp_advertising);
+	__ETHTOOL_DECLARE_LINK_MODE_MASK(advertising);
+	enum ethtool_link_mode_bit_indices resolved;
+	struct mtip_backplane *priv = phydev->priv;
+	__ETHTOOL_DECLARE_LINK_MODE_MASK(common);
+	u64 base_page, lpa;
+	int err;
+
+	err = mtip_state_reset(phydev);
+	if (err)
+		return err;
+
+	err = mtip_read_adv(phydev, &base_page);
+	if (err < 0)
+		return err;
+
+	err = mtip_read_lpa(phydev, &lpa);
+	if (err < 0)
+		return err;
+
+	if (lpa & C73_BASE_PAGE_NP)
+		phydev_warn(phydev, "Next Page exchange not implemented!\n");
+
+	mii_c73_mod_linkmode_lpa_t(advertising, base_page);
+	mii_c73_mod_linkmode_lpa_t(lp_advertising, lpa);
+	linkmode_and(common, advertising, lp_advertising);
+
+	err = linkmode_c73_priority_resolution(common, &resolved);
+	if (err) {
+		phydev_dbg(phydev, "C73 page received, no common link mode\n");
+		return 0;
+	}
+
+	err = mtip_wait_bp_eth_stat(phydev, resolved);
+	if (err) {
+		*restart_an = true;
+		return 0;
+	}
+
+	phydev_dbg(phydev,
+		   "C73 page received, LD %04x:%04x:%04x, LP %04x:%04x:%04x, resolved link mode %s\n",
+		   C73_ADV_2(base_page), C73_ADV_1(base_page), C73_ADV_0(base_page),
+		   C73_ADV_2(lpa), C73_ADV_1(lpa), C73_ADV_0(lpa),
+		   ethtool_link_mode_str(resolved));
+
+	err = phy_set_mode_ext(priv->serdes, PHY_MODE_ETHERNET_PHY, resolved);
+	if (err) {
+		phydev_err(phydev, "phy_set_mode_ext(%s) returned %pe\n",
+			   ethtool_link_mode_str(resolved), ERR_PTR(err));
+		return err;
+	}
+
+	err = mtip_wait_for_cdr_lock(phydev);
+	if (err)
+		phydev_warn(phydev, "Failed to reacquire CDR lock after protocol change: %pe\n",
+			    ERR_PTR(err));
+
+	if (link_mode_needs_training(resolved)) {
+		err = mtip_start_lt(phydev);
+		if (err)
+			return err;
+	} else {
+		/* Allow the datapath to come up without link training */
+		err = mtip_modify_lt(phydev, LT_STAT, LT_STAT_RX_STATUS,
+				     LT_STAT_RX_STATUS);
+		if (err < 0)
+			return err;
+	}
+
+	priv->link_mode = resolved;
+	priv->link_mode_resolved = true;
+
+	return 0;
+}
+
+static void mtip_c73_remote_fault(struct phy_device *phydev, bool fault)
+{
+	phydev_err(phydev, "Remote fault: %d\n", fault);
+}
+
+static void mtip_irqpoll_work(struct work_struct *work)
+{
+	struct mtip_irqpoll *irqpoll = container_of(work, struct mtip_irqpoll, work.work);
+	struct phy_device *phydev = irqpoll->phydev;
+	struct mtip_backplane *priv = phydev->priv;
+	bool restart_an = false;
+	int val, err = 0;
+	int pcs_stat = 0;
+	bool cdr_locked;
+
+	/* Check for AN restart requests from the link training kthreads */
+	mutex_lock(&priv->an_restart_lock);
+	if (priv->an_restart_pending) {
+		restart_an = true;
+		priv->an_restart_pending = false;
+	}
+	mutex_unlock(&priv->an_restart_lock);
+
+	/* Then enter the irqpoll logic per se
+	 * (PCS MDIO_STAT1, AN/LT MDIO_STAT1 and CDR lock)
+	 */
+	mutex_lock(&irqpoll->lock);
+
+	err = phy_check_cdr_lock(priv->serdes, &cdr_locked);
+	if (err)
+		goto out_unlock;
+
+	if (priv->link_mode_resolved) {
+		pcs_stat = mtip_read_pcs(phydev, MDIO_STAT1);
+		if (pcs_stat < 0) {
+			err = pcs_stat;
+			goto out_unlock;
+		}
+	}
+
+	val = mtip_read_an(phydev, AN_STAT);
+	if (val < 0) {
+		err = val;
+		goto out_unlock;
+	}
+
+	if ((irqpoll->cdr_locked != cdr_locked) ||
+	    ((irqpoll->old_an_stat ^ val) & (MDIO_STAT1_LSTATUS |
+					     MDIO_AN_STAT1_COMPLETE)) ||
+	    ((irqpoll->old_pcs_stat ^ pcs_stat) & MDIO_STAT1_LSTATUS)) {
+		mtip_update_link_latch(phydev, cdr_locked,
+				       !!(val & MDIO_STAT1_LSTATUS),
+				       !!(val & MDIO_AN_STAT1_COMPLETE),
+				       !!(pcs_stat & MDIO_STAT1_LSTATUS));
+	}
+
+	/* The manual says that this bit is latched high, but experimentation
+	 * shows that reads will not unlatch it while link training is in
+	 * progress; only reading it after link training has completed will.
+	 * Only act upon bit transitions, to avoid processing a false "page
+	 * received" event during link training.
+	 */
+	if (((irqpoll->old_an_stat ^ val) & MDIO_AN_STAT1_PAGE) &&
+	    (val & MDIO_AN_STAT1_PAGE)) {
+		err = mtip_c73_page_received(phydev, &restart_an);
+		if (err)
+			goto out_unlock;
+	}
+
+	if ((irqpoll->old_an_stat ^ val) & MDIO_AN_STAT1_RFAULT)
+		mtip_c73_remote_fault(phydev, val & MDIO_AN_STAT1_RFAULT);
+
+	/* Checks that result in AN restart should go at the end */
+
+	/* Make sure the lane goes back into DME page exchange mode
+	 * after a link drop
+	 */
+	if (priv->link_mode_resolved &&
+	    (irqpoll->old_pcs_stat & MDIO_STAT1_LSTATUS) &&
+	    !(pcs_stat & MDIO_STAT1_LSTATUS)) {
+		phydev_dbg(phydev, "PCS link dropped, restarting autoneg\n");
+		restart_an = true;
+	}
+
+	/* Paranoid workaround for undetermined issue */
+	if (!priv->link_mode_resolved && (val & MDIO_AN_STAT1_COMPLETE) &&
+	    priv->an_enabled && time_after(jiffies, priv->last_an_restart +
+					   msecs_to_jiffies(MTIP_AN_TIMEOUT_MS))) {
+		phydev_err(phydev,
+			   "Hardware says AN has completed, but we never saw a base page, and that's bogus\n");
+		restart_an = true;
+	}
+
+	if (restart_an) {
+		err = mtip_an_restart(phydev);
+		if (err)
+			goto out_unlock;
+
+		/* don't overwrite what was set by mtip_unlatch_an_stat() */
+		goto ignore_an_and_pcs_stat;
+	}
+
+	irqpoll->old_an_stat = val;
+	irqpoll->old_pcs_stat = pcs_stat;
+ignore_an_and_pcs_stat:
+	irqpoll->cdr_locked = cdr_locked;
+
+out_unlock:
+	mutex_unlock(&irqpoll->lock);
+
+	if (err) {
+		phy_error(phydev);
+		return;
+	}
+
+	schedule_delayed_work(&irqpoll->work, IRQPOLL_INTERVAL);
+}
+
+static int mtip_parse_dt(struct phy_device *phydev)
+{
+	struct device_node *dn = phydev->mdio.dev.of_node;
+	struct mtip_backplane *priv = phydev->priv;
+	struct device_node *pcs_node;
+
+	priv->serdes = of_phy_get(dn, NULL);
+	if (IS_ERR(priv->serdes))
+		return PTR_ERR(priv->serdes);
+
+	pcs_node = of_parse_phandle(dn, "pcs-handle", 0);
+	if (pcs_node) {
+		if (!of_device_is_available(pcs_node)) {
+			phydev_err(phydev, "pcs-handle node not available\n");
+			of_node_put(pcs_node);
+			return -ENODEV;
+		}
+
+		priv->pcs = of_mdio_find_device(pcs_node);
+		of_node_put(pcs_node);
+		if (!priv->pcs) {
+			phydev_err(phydev, "missing PCS device\n");
+			return -EPROBE_DEFER;
+		}
+	} else {
+		priv->pcs = &phydev->mdio;
+	}
+
+	return 0;
+}
+
+static bool mtip_is_lx2160a(struct phy_device *phydev)
+{
+	return of_device_is_compatible(phydev->mdio.dev.of_node,
+				       "fsl,lx2160a-backplane-anlt");
+}
+
+static int mtip_lx2160a_match_phy_device(struct phy_device *phydev)
+{
+	return mtip_is_lx2160a(phydev);
+}
+
+static void mtip_irqpoll_init(struct phy_device *phydev,
+			      struct mtip_irqpoll *irqpoll)
+{
+	mutex_init(&irqpoll->lock);
+	INIT_DELAYED_WORK(&irqpoll->work, mtip_irqpoll_work);
+	irqpoll->phydev = phydev;
+}
+
+static void mtip_start_irqpoll(struct phy_device *phydev)
+{
+	struct mtip_irqpoll *irqpoll = phydev_to_irqpoll(phydev);
+
+	schedule_delayed_work(&irqpoll->work, 0);
+}
+
+static void mtip_stop_irqpoll(struct phy_device *phydev)
+{
+	struct mtip_irqpoll *irqpoll = phydev_to_irqpoll(phydev);
+
+	cancel_delayed_work_sync(&irqpoll->work);
+}
+
+static int mtip_probe(struct phy_device *phydev)
+{
+	struct device *dev = &phydev->mdio.dev;
+	struct mtip_backplane *priv;
+	int err;
+
+	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
+	if (!priv) {
+		err = -ENOMEM;
+		goto out;
+	}
+
+	phydev->port = PORT_DA;
+
+	if (mtip_is_lx2160a(phydev)) {
+		priv->an_regs = mtip_lx2160a_an_regs;
+		priv->lt_regs = mtip_lx2160a_lt_regs;
+		priv->lt_mmd = MDIO_MMD_AN;
+	} /* else TODO */
+
+	mtip_irqpoll_init(phydev, &priv->irqpoll);
+	mutex_init(&priv->an_restart_lock);
+	mutex_init(&priv->lt_lock);
+	phydev->priv = priv;
+
+	priv->local_tx_lt_worker = kthread_create_worker(0, "%s_local_tx_lt",
+							 dev_name(dev));
+	if (IS_ERR(priv->local_tx_lt_worker)) {
+		err = PTR_ERR(priv->local_tx_lt_worker);
+		goto out_free_priv;
+	}
+
+	priv->remote_tx_lt_worker = kthread_create_worker(0, "%s_remote_tx_lt",
+							  dev_name(dev));
+	if (IS_ERR(priv->remote_tx_lt_worker)) {
+		err = PTR_ERR(priv->remote_tx_lt_worker);
+		goto out_destroy_local_tx_lt;
+	}
+
+	err = mtip_parse_dt(phydev);
+	if (err)
+		goto out_destroy_remote_tx_lt;
+
+	err = phy_init(priv->serdes);
+	if (err) {
+		phydev_err(phydev, "Failed to initialize SerDes: %pe\n",
+			   ERR_PTR(err));
+		goto out_put_phy;
+	}
+
+	mtip_start_irqpoll(phydev);
+
+	return 0;
+
+out_put_phy:
+	of_phy_put(priv->serdes);
+out_destroy_remote_tx_lt:
+	kthread_destroy_worker(priv->remote_tx_lt_worker);
+out_destroy_local_tx_lt:
+	kthread_destroy_worker(priv->local_tx_lt_worker);
+out_free_priv:
+	kfree(priv);
+out:
+	return err;
+}
+
+static void mtip_remove(struct phy_device *phydev)
+{
+	struct mtip_backplane *priv = phydev->priv;
+
+	mtip_stop_irqpoll(phydev);
+	phy_exit(priv->serdes);
+	of_phy_put(priv->serdes);
+	kthread_destroy_worker(priv->remote_tx_lt_worker);
+	kthread_destroy_worker(priv->local_tx_lt_worker);
+	kfree(priv);
+}
+
+static int mtip_config_aneg(struct phy_device *phydev)
+{
+	u16 mask = MDIO_AN_CTRL1_ENABLE | MDIO_AN_CTRL1_RESTART;
+	struct mtip_irqpoll *irqpoll = phydev_to_irqpoll(phydev);
+	struct mtip_backplane *priv = phydev->priv;
+	int err;
+
+	mutex_lock(&irqpoll->lock);
+
+	/* We support anything */
+	phydev->master_slave_get = phydev->master_slave_set;
+
+	/* Only allow advertising what this PHY supports. The device tree
+	 * property "max-speed" may further limit the speed and thus the
+	 * link modes. Similar to genphy_config_advert().
+	 */
+	linkmode_and(phydev->advertising, phydev->advertising,
+		     phydev->supported);
+
+	if (phydev->autoneg == AUTONEG_ENABLE) {
+		err = mtip_an_restart(phydev);
+		if (err)
+			goto out_unlock;
+
+		priv->an_enabled = true;
+	} else {
+		err = mtip_modify_an(phydev, AN_CTRL, mask, 0);
+		if (err < 0)
+			goto out_unlock;
+
+		priv->an_enabled = false;
+	}
+
+out_unlock:
+	mutex_unlock(&irqpoll->lock);
+
+	return err;
+}
+
+static int mtip_resolve_aneg_linkmode(struct phy_device *phydev)
+{
+	u64 base_page;
+	int err;
+
+	linkmode_zero(phydev->lp_advertising);
+
+	err = mtip_read_lpa(phydev, &base_page);
+	if (err)
+		return err;
+
+	mii_c73_mod_linkmode_lpa_t(phydev->lp_advertising, base_page);
+	phy_resolve_aneg_linkmode(phydev);
+
+	return 0;
+}
+
+static int mtip_read_status(struct phy_device *phydev)
+{
+	struct mtip_irqpoll *irqpoll = phydev_to_irqpoll(phydev);
+	u64 base_page;
+	int err = 0;
+
+	mutex_lock(&irqpoll->lock);
+
+	err = mtip_read_adv(phydev, &base_page);
+	if (err)
+		goto out_unlock;
+
+	if (C73_BASE_PAGE_TRANSMITTED_NONCE_X(base_page) & BIT(4))
+		phydev->master_slave_state = MASTER_SLAVE_STATE_MASTER;
+	else
+		phydev->master_slave_state = MASTER_SLAVE_STATE_SLAVE;
+
+	phydev->speed = SPEED_UNKNOWN;
+	phydev->duplex = DUPLEX_UNKNOWN;
+	phydev->pause = 0;
+	phydev->asym_pause = 0;
+
+	phydev->link = mtip_read_link_unlatch(phydev);
+	if (!phydev->link)
+		goto out_unlock;
+
+	if (phydev->autoneg == AUTONEG_ENABLE) {
+		phydev->autoneg_complete = mtip_cached_an_complete(phydev);
+
+		if (phydev->autoneg_complete)
+			err = mtip_resolve_aneg_linkmode(phydev);
+	}
+
+out_unlock:
+	mutex_unlock(&irqpoll->lock);
+
+	return err;
+}
+
+static int mtip_suspend(struct phy_device *phydev)
+{
+	struct mtip_backplane *priv = phydev->priv;
+	int err;
+
+	err = phy_power_off(priv->serdes);
+	if (err) {
+		phydev_err(phydev, "Failed to power off SerDes: %pe\n",
+			   ERR_PTR(err));
+		return err;
+	}
+
+	return 0;
+}
+
+static int mtip_resume(struct phy_device *phydev)
+{
+	struct mtip_backplane *priv = phydev->priv;
+	int err;
+
+	err = phy_power_on(priv->serdes);
+	if (err) {
+		phydev_err(phydev, "Failed to power on SerDes: %pe\n",
+			   ERR_PTR(err));
+		return err;
+	}
+
+	return 0;
+}
+
+static int mtip_config_init(struct phy_device *phydev)
+{
+	int err;
+
+	err = mtip_reset_an(phydev);
+	if (err < 0)
+		return err;
+
+	err = mtip_reset_pcs(phydev);
+	if (err < 0)
+		return err;
+
+	return 0;
+}
+
+static struct phy_driver mtip_backplane_driver[] = {
+	{
+		.match_phy_device	= mtip_lx2160a_match_phy_device,
+		.flags			= PHY_IS_INTERNAL,
+		.name			= "MTIP AN/LT",
+		.probe			= mtip_probe,
+		.remove			= mtip_remove,
+		.get_features		= mtip_lx2160a_get_features,
+		.suspend		= mtip_suspend,
+		.resume			= mtip_resume,
+		.config_aneg		= mtip_config_aneg,
+		.read_status		= mtip_read_status,
+		.config_init		= mtip_config_init,
+	},
+};
+
+static const struct of_device_id __maybe_unused mtip_backplane_of_match[] = {
+	{ .compatible = "fsl,lx2160a-backplane-anlt" },
+	{ /* sentinel */ },
+};
+MODULE_DEVICE_TABLE(of, mtip_backplane_of_match);
+
+module_phy_driver(mtip_backplane_driver);
+
+MODULE_AUTHOR("Vladimir Oltean <vladimir.oltean@xxxxxxx>");
+MODULE_DESCRIPTION("MTIP Backplane PHY driver");
+MODULE_LICENSE("GPL");
-- 
2.34.1