net: tn40xx: add mdio bus support

This patch adds supports for mdio bus. A later path adds PHYLIB
support on the top of this.
Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
Link: https://patch.msgid.link/20240623235507.108147-7-fujita.tomonori@gmail.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/tehuti/Makefile

@@ -5,5 +5,5 @@
 
 obj-$(CONFIG_TEHUTI) += tehuti.o
 
-tn40xx-y := tn40.o
+tn40xx-y := tn40.o tn40_mdio.o
 obj-$(CONFIG_TEHUTI_TN40) += tn40xx.o

drivers/net/ethernet/tehuti/tn40.h

@@ -140,6 +140,8 @@ struct tn40_priv {
 	u32 b0_len;
 	dma_addr_t b0_dma; /* Physical address of buffer */
 	char *b0_va; /* Virtual address of buffer */
+
+	struct mii_bus *mdio;
 };
 
 /* RX FREE descriptor - 64bit */
@@ -217,4 +219,6 @@ static inline void tn40_write_reg(struct tn40_priv *priv, u32 reg, u32 val)
 	writel(val, priv->regs + reg);
 }
 
+int tn40_mdiobus_init(struct tn40_priv *priv);
+
 #endif /* _TN40XX_H */

drivers/net/ethernet/tehuti/tn40_mdio.c

+// SPDX-License-Identifier: GPL-2.0+
+/* Copyright (c) Tehuti Networks Ltd. */
+
+#include <linux/netdevice.h>
+#include <linux/pci.h>
+#include <linux/phylink.h>
+
+#include "tn40.h"
+
+#define TN40_MDIO_DEVAD_MASK GENMASK(4, 0)
+#define TN40_MDIO_PRTAD_MASK GENMASK(9, 5)
+#define TN40_MDIO_CMD_VAL(device, port)			\
+	(FIELD_PREP(TN40_MDIO_DEVAD_MASK, (device)) |	\
+	 (FIELD_PREP(TN40_MDIO_PRTAD_MASK, (port))))
+#define TN40_MDIO_CMD_READ BIT(15)
+
+static void tn40_mdio_set_speed(struct tn40_priv *priv, u32 speed)
+{
+	void __iomem *regs = priv->regs;
+	int mdio_cfg;
+
+	if (speed == TN40_MDIO_SPEED_1MHZ)
+		mdio_cfg = (0x7d << 7) | 0x08;	/* 1MHz */
+	else
+		mdio_cfg = 0xA08;	/* 6MHz */
+	mdio_cfg |= (1 << 6);
+	writel(mdio_cfg, regs + TN40_REG_MDIO_CMD_STAT);
+	msleep(100);
+}
+
+static u32 tn40_mdio_stat(struct tn40_priv *priv)
+{
+	void __iomem *regs = priv->regs;
+
+	return readl(regs + TN40_REG_MDIO_CMD_STAT);
+}
+
+static int tn40_mdio_wait_nobusy(struct tn40_priv *priv, u32 *val)
+{
+	u32 stat;
+	int ret;
+
+	ret = readx_poll_timeout_atomic(tn40_mdio_stat, priv, stat,
+					TN40_GET_MDIO_BUSY(stat) == 0, 10,
+					10000);
+	if (val)
+		*val = stat;
+	return ret;
+}
+
+static int tn40_mdio_read(struct tn40_priv *priv, int port, int device,
+			  u16 regnum)
+{
+	void __iomem *regs = priv->regs;
+	u32 i;
+
+	/* wait until MDIO is not busy */
+	if (tn40_mdio_wait_nobusy(priv, NULL))
+		return -EIO;
+
+	i = TN40_MDIO_CMD_VAL(device, port);
+	writel(i, regs + TN40_REG_MDIO_CMD);
+	writel((u32)regnum, regs + TN40_REG_MDIO_ADDR);
+	if (tn40_mdio_wait_nobusy(priv, NULL))
+		return -EIO;
+
+	writel(TN40_MDIO_CMD_READ | i, regs + TN40_REG_MDIO_CMD);
+	/* read CMD_STAT until not busy */
+	if (tn40_mdio_wait_nobusy(priv, NULL))
+		return -EIO;
+
+	return lower_16_bits(readl(regs + TN40_REG_MDIO_DATA));
+}
+
+static int tn40_mdio_write(struct tn40_priv *priv, int port, int device,
+			   u16 regnum, u16 data)
+{
+	void __iomem *regs = priv->regs;
+	u32 tmp_reg = 0;
+	int ret;
+
+	/* wait until MDIO is not busy */
+	if (tn40_mdio_wait_nobusy(priv, NULL))
+		return -EIO;
+	writel(TN40_MDIO_CMD_VAL(device, port), regs + TN40_REG_MDIO_CMD);
+	writel((u32)regnum, regs + TN40_REG_MDIO_ADDR);
+	if (tn40_mdio_wait_nobusy(priv, NULL))
+		return -EIO;
+	writel((u32)data, regs + TN40_REG_MDIO_DATA);
+	/* read CMD_STAT until not busy */
+	ret = tn40_mdio_wait_nobusy(priv, &tmp_reg);
+	if (ret)
+		return -EIO;
+
+	if (TN40_GET_MDIO_RD_ERR(tmp_reg)) {
+		dev_err(&priv->pdev->dev, "MDIO error after write command\n");
+		return -EIO;
+	}
+	return 0;
+}
+
+static int tn40_mdio_read_c45(struct mii_bus *mii_bus, int addr, int devnum,
+			      int regnum)
+{
+	return tn40_mdio_read(mii_bus->priv, addr, devnum, regnum);
+}
+
+static int tn40_mdio_write_c45(struct mii_bus *mii_bus, int addr, int devnum,
+			       int regnum, u16 val)
+{
+	return  tn40_mdio_write(mii_bus->priv, addr, devnum, regnum, val);
+}
+
+int tn40_mdiobus_init(struct tn40_priv *priv)
+{
+	struct pci_dev *pdev = priv->pdev;
+	struct mii_bus *bus;
+	int ret;
+
+	bus = devm_mdiobus_alloc(&pdev->dev);
+	if (!bus)
+		return -ENOMEM;
+
+	bus->name = TN40_DRV_NAME;
+	bus->parent = &pdev->dev;
+	snprintf(bus->id, MII_BUS_ID_SIZE, "tn40xx-%x-%x",
+		 pci_domain_nr(pdev->bus), pci_dev_id(pdev));
+	bus->priv = priv;
+
+	bus->read_c45 = tn40_mdio_read_c45;
+	bus->write_c45 = tn40_mdio_write_c45;
+
+	ret = devm_mdiobus_register(&pdev->dev, bus);
+	if (ret) {
+		dev_err(&pdev->dev, "failed to register mdiobus %d %u %u\n",
+			ret, bus->state, MDIOBUS_UNREGISTERED);
+		return ret;
+	}
+	tn40_mdio_set_speed(priv, TN40_MDIO_SPEED_6MHZ);
+	priv->mdio = bus;
+	return 0;
+}