drivers/net/mdio/mdio-ipq4019.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause
 /* Copyright (c) 2015, The Linux Foundation. All rights reserved. */
 /* Copyright (c) 2020 Sartura Ltd. */

 #include <linux/delay.h>
 #include <linux/io.h>
 #include <linux/iopoll.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/of_address.h>
 #include <linux/of_mdio.h>
 #include <linux/phy.h>
 #include <linux/platform_device.h>
 #include <linux/clk.h>

 #define MDIO_MODE_REG				0x40
 #define   MDIO_MODE_MDC_MODE			BIT(12)
 /* 0 = Clause 22, 1 = Clause 45 */
 #define   MDIO_MODE_C45				BIT(8)
 #define   MDIO_MODE_DIV_MASK			GENMASK(7, 0)
 #define     MDIO_MODE_DIV(x)			FIELD_PREP(MDIO_MODE_DIV_MASK, (x) - 1)
 #define     MDIO_MODE_DIV_1			0x0
 #define     MDIO_MODE_DIV_2			0x1
 #define     MDIO_MODE_DIV_4			0x3
 #define     MDIO_MODE_DIV_8			0x7
 #define     MDIO_MODE_DIV_16			0xf
 #define     MDIO_MODE_DIV_32			0x1f
 #define     MDIO_MODE_DIV_64			0x3f
 #define     MDIO_MODE_DIV_128			0x7f
 #define     MDIO_MODE_DIV_256			0xff
 #define MDIO_ADDR_REG				0x44
 #define MDIO_DATA_WRITE_REG			0x48
 #define MDIO_DATA_READ_REG			0x4c
 #define MDIO_CMD_REG				0x50
 #define MDIO_CMD_ACCESS_BUSY		BIT(16)
 #define MDIO_CMD_ACCESS_START		BIT(8)
 #define MDIO_CMD_ACCESS_CODE_READ	0
 #define MDIO_CMD_ACCESS_CODE_WRITE	1
 #define MDIO_CMD_ACCESS_CODE_C45_ADDR	0
 #define MDIO_CMD_ACCESS_CODE_C45_WRITE	1
 #define MDIO_CMD_ACCESS_CODE_C45_READ	2

 #define IPQ4019_MDIO_TIMEOUT	10000
 #define IPQ4019_MDIO_SLEEP		10

 /* MDIO clock source frequency is fixed to 100M */
 #define IPQ_MDIO_CLK_RATE	100000000

 #define IPQ_PHY_SET_DELAY_US	100000

 struct ipq4019_mdio_data {
 	void __iomem	*membase;
 	void __iomem *eth_ldo_rdy;
 	struct clk *mdio_clk;
 	unsigned int mdc_rate;
 };

 static int ipq4019_mdio_wait_busy(struct mii_bus *bus)
 {
 	struct ipq4019_mdio_data *priv = bus->priv;
 	unsigned int busy;

 	return readl_poll_timeout(priv->membase + MDIO_CMD_REG, busy,
 				  (busy & MDIO_CMD_ACCESS_BUSY) == 0,
 				  IPQ4019_MDIO_SLEEP, IPQ4019_MDIO_TIMEOUT);
 }

 static int ipq4019_mdio_read_c45(struct mii_bus *bus, int mii_id, int mmd,
 				 int reg)
 {
 	struct ipq4019_mdio_data *priv = bus->priv;
 	unsigned int data;
 	unsigned int cmd;

 	if (ipq4019_mdio_wait_busy(bus))
 		return -ETIMEDOUT;

 	data = readl(priv->membase + MDIO_MODE_REG);

 	data |= MDIO_MODE_C45;

 	writel(data, priv->membase + MDIO_MODE_REG);

 	/* issue the phy address and mmd */
 	writel((mii_id << 8) | mmd, priv->membase + MDIO_ADDR_REG);

 	/* issue reg */
 	writel(reg, priv->membase + MDIO_DATA_WRITE_REG);

 	cmd = MDIO_CMD_ACCESS_START | MDIO_CMD_ACCESS_CODE_C45_ADDR;

 	/* issue read command */
 	writel(cmd, priv->membase + MDIO_CMD_REG);

 	/* Wait read complete */
 	if (ipq4019_mdio_wait_busy(bus))
 		return -ETIMEDOUT;

 	cmd = MDIO_CMD_ACCESS_START | MDIO_CMD_ACCESS_CODE_C45_READ;

 	writel(cmd, priv->membase + MDIO_CMD_REG);

 	if (ipq4019_mdio_wait_busy(bus))
 		return -ETIMEDOUT;

 	/* Read and return data */
 	return readl(priv->membase + MDIO_DATA_READ_REG);
 }

 static int ipq4019_mdio_read_c22(struct mii_bus *bus, int mii_id, int regnum)
 {
 	struct ipq4019_mdio_data *priv = bus->priv;
 	unsigned int data;
 	unsigned int cmd;

 	if (ipq4019_mdio_wait_busy(bus))
 		return -ETIMEDOUT;

 	data = readl(priv->membase + MDIO_MODE_REG);

 	data &= ~MDIO_MODE_C45;

 	writel(data, priv->membase + MDIO_MODE_REG);

 	/* issue the phy address and reg */
 	writel((mii_id << 8) | regnum, priv->membase + MDIO_ADDR_REG);

 	cmd = MDIO_CMD_ACCESS_START | MDIO_CMD_ACCESS_CODE_READ;

 	/* issue read command */
 	writel(cmd, priv->membase + MDIO_CMD_REG);

 	/* Wait read complete */
 	if (ipq4019_mdio_wait_busy(bus))
 		return -ETIMEDOUT;

 	/* Read and return data */
 	return readl(priv->membase + MDIO_DATA_READ_REG);
 }

 static int ipq4019_mdio_write_c45(struct mii_bus *bus, int mii_id, int mmd,
 				  int reg, u16 value)
 {
 	struct ipq4019_mdio_data *priv = bus->priv;
 	unsigned int data;
 	unsigned int cmd;

 	if (ipq4019_mdio_wait_busy(bus))
 		return -ETIMEDOUT;

 	data = readl(priv->membase + MDIO_MODE_REG);

 	data |= MDIO_MODE_C45;

 	writel(data, priv->membase + MDIO_MODE_REG);

 	/* issue the phy address and mmd */
 	writel((mii_id << 8) | mmd, priv->membase + MDIO_ADDR_REG);

 	/* issue reg */
 	writel(reg, priv->membase + MDIO_DATA_WRITE_REG);

 	cmd = MDIO_CMD_ACCESS_START | MDIO_CMD_ACCESS_CODE_C45_ADDR;

 	writel(cmd, priv->membase + MDIO_CMD_REG);

 	if (ipq4019_mdio_wait_busy(bus))
 		return -ETIMEDOUT;

 	/* issue write data */
 	writel(value, priv->membase + MDIO_DATA_WRITE_REG);

 	cmd = MDIO_CMD_ACCESS_START | MDIO_CMD_ACCESS_CODE_C45_WRITE;
 	writel(cmd, priv->membase + MDIO_CMD_REG);

 	/* Wait write complete */
 	if (ipq4019_mdio_wait_busy(bus))
 		return -ETIMEDOUT;

 	return 0;
 }

 static int ipq4019_mdio_write_c22(struct mii_bus *bus, int mii_id, int regnum,
 				  u16 value)
 {
 	struct ipq4019_mdio_data *priv = bus->priv;
 	unsigned int data;
 	unsigned int cmd;

 	if (ipq4019_mdio_wait_busy(bus))
 		return -ETIMEDOUT;

 	/* Enter Clause 22 mode */
 	data = readl(priv->membase + MDIO_MODE_REG);

 	data &= ~MDIO_MODE_C45;

 	writel(data, priv->membase + MDIO_MODE_REG);

 	/* issue the phy address and reg */
 	writel((mii_id << 8) | regnum, priv->membase + MDIO_ADDR_REG);

 	/* issue write data */
 	writel(value, priv->membase + MDIO_DATA_WRITE_REG);

 	/* issue write command */
 	cmd = MDIO_CMD_ACCESS_START | MDIO_CMD_ACCESS_CODE_WRITE;

 	writel(cmd, priv->membase + MDIO_CMD_REG);

 	/* Wait write complete */
 	if (ipq4019_mdio_wait_busy(bus))
 		return -ETIMEDOUT;

 	return 0;
 }

 static int ipq4019_mdio_set_div(struct ipq4019_mdio_data *priv)
 {
 	unsigned long ahb_rate;
 	int div;
 	u32 val;

 	/* If we don't have a clock for AHB use the fixed value */
 	ahb_rate = IPQ_MDIO_CLK_RATE;
 	if (priv->mdio_clk)
 		ahb_rate = clk_get_rate(priv->mdio_clk);

 	/* MDC rate is ahb_rate/(MDIO_MODE_DIV + 1)
 	 * While supported, internal documentation doesn't
 	 * assure correct functionality of the MDIO bus
 	 * with divider of 1, 2 or 4.
 	 */
 	for (div = 8; div <= 256; div *= 2) {
 		/* The requested rate is supported by the div */
 		if (priv->mdc_rate == DIV_ROUND_UP(ahb_rate, div)) {
 			val = readl(priv->membase + MDIO_MODE_REG);
 			val &= ~MDIO_MODE_DIV_MASK;
 			val |= MDIO_MODE_DIV(div);
 			writel(val, priv->membase + MDIO_MODE_REG);

 			return 0;
 		}
 	}

 	/* The requested rate is not supported */
 	return -EINVAL;
 }

 static int ipq_mdio_reset(struct mii_bus *bus)
 {
 	struct ipq4019_mdio_data *priv = bus->priv;
 	u32 val;
 	int ret;

 	/* To indicate CMN_PLL that ethernet_ldo has been ready if platform resource 1
 	 * is specified in the device tree.
 	 */
 	if (priv->eth_ldo_rdy) {
 		val = readl(priv->eth_ldo_rdy);
 		val |= BIT(0);
 		writel(val, priv->eth_ldo_rdy);
 		fsleep(IPQ_PHY_SET_DELAY_US);
 	}

 	/* Configure MDIO clock source frequency if clock is specified in the device tree */
 	ret = clk_set_rate(priv->mdio_clk, IPQ_MDIO_CLK_RATE);
 	if (ret)
 		return ret;

 	ret = clk_prepare_enable(priv->mdio_clk);
 	if (ret)
 		return ret;

 	mdelay(10);

 	/* Restore MDC rate */
 	return ipq4019_mdio_set_div(priv);
 }

 static void ipq4019_mdio_select_mdc_rate(struct platform_device *pdev,
 					 struct ipq4019_mdio_data *priv)
 {
 	unsigned long ahb_rate;
 	int div;
 	u32 val;

 	/* MDC rate defined in DT, we don't have to decide a default value */
 	if (!of_property_read_u32(pdev->dev.of_node, "clock-frequency",
 				  &priv->mdc_rate))
 		return;

 	/* If we don't have a clock for AHB use the fixed value */
 	ahb_rate = IPQ_MDIO_CLK_RATE;
 	if (priv->mdio_clk)
 		ahb_rate = clk_get_rate(priv->mdio_clk);

 	/* Check what is the current div set */
 	val = readl(priv->membase + MDIO_MODE_REG);
 	div = FIELD_GET(MDIO_MODE_DIV_MASK, val);

 	/* div is not set to the default value of /256
 	 * Probably someone changed that (bootloader, other drivers)
 	 * Keep this and don't overwrite it.
 	 */
 	if (div != MDIO_MODE_DIV_256) {
 		priv->mdc_rate = DIV_ROUND_UP(ahb_rate, div + 1);
 		return;
 	}

 	/* If div is /256 assume nobody have set this value and
 	 * try to find one MDC rate that is close the 802.3 spec of
 	 * 2.5MHz
 	 */
 	for (div = 256; div >= 8; div /= 2) {
 		/* Stop as soon as we found a divider that
 		 * reached the closest value to 2.5MHz
 		 */
 		if (DIV_ROUND_UP(ahb_rate, div) > 2500000)
 			break;

 		priv->mdc_rate = DIV_ROUND_UP(ahb_rate, div);
 	}
 }

 static int ipq4019_mdio_probe(struct platform_device *pdev)
 {
 	struct ipq4019_mdio_data *priv;
 	struct mii_bus *bus;
 	struct resource *res;
 	int ret;

 	bus = devm_mdiobus_alloc_size(&pdev->dev, sizeof(*priv));
 	if (!bus)
 		return -ENOMEM;

 	priv = bus->priv;

 	priv->membase = devm_platform_ioremap_resource(pdev, 0);
 	if (IS_ERR(priv->membase))
 		return PTR_ERR(priv->membase);

 	priv->mdio_clk = devm_clk_get_optional(&pdev->dev, "gcc_mdio_ahb_clk");
 	if (IS_ERR(priv->mdio_clk))
 		return PTR_ERR(priv->mdio_clk);

 	ipq4019_mdio_select_mdc_rate(pdev, priv);
 	ret = ipq4019_mdio_set_div(priv);
 	if (ret)
 		return ret;

 	/* The platform resource is provided on the chipset IPQ5018 */
 	/* This resource is optional */
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 1);
 	if (res)
 		priv->eth_ldo_rdy = devm_ioremap_resource(&pdev->dev, res);

 	bus->name = "ipq4019_mdio";
 	bus->read = ipq4019_mdio_read_c22;
 	bus->write = ipq4019_mdio_write_c22;
 	bus->read_c45 = ipq4019_mdio_read_c45;
 	bus->write_c45 = ipq4019_mdio_write_c45;
 	bus->reset = ipq_mdio_reset;
 	bus->parent = &pdev->dev;
 	snprintf(bus->id, MII_BUS_ID_SIZE, "%s%d", pdev->name, pdev->id);

 	ret = of_mdiobus_register(bus, pdev->dev.of_node);
 	if (ret) {
 		dev_err(&pdev->dev, "Cannot register MDIO bus!\n");
 		return ret;
 	}

 	platform_set_drvdata(pdev, bus);

 	return 0;
 }

 static void ipq4019_mdio_remove(struct platform_device *pdev)
 {
 	struct mii_bus *bus = platform_get_drvdata(pdev);

 	mdiobus_unregister(bus);
 }

 static const struct of_device_id ipq4019_mdio_dt_ids[] = {
 	{ .compatible = "qcom,ipq4019-mdio" },
 	{ .compatible = "qcom,ipq5018-mdio" },
 	{ }
 };
 MODULE_DEVICE_TABLE(of, ipq4019_mdio_dt_ids);

 static struct platform_driver ipq4019_mdio_driver = {
 	.probe = ipq4019_mdio_probe,
 	.remove_new = ipq4019_mdio_remove,
 	.driver = {
 		.name = "ipq4019-mdio",
 		.of_match_table = ipq4019_mdio_dt_ids,
 	},
 };

 module_platform_driver(ipq4019_mdio_driver);

 MODULE_DESCRIPTION("ipq4019 MDIO interface driver");
 MODULE_AUTHOR("Qualcomm Atheros");
 MODULE_LICENSE("Dual BSD/GPL");
	// SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause
	/* Copyright (c) 2015, The Linux Foundation. All rights reserved. */
	/* Copyright (c) 2020 Sartura Ltd. */

	#include <linux/delay.h>
	#include <linux/io.h>
	#include <linux/iopoll.h>
	#include <linux/kernel.h>
	#include <linux/module.h>
	#include <linux/of_address.h>
	#include <linux/of_mdio.h>
	#include <linux/phy.h>
	#include <linux/platform_device.h>
	#include <linux/clk.h>

	#define MDIO_MODE_REG 0x40
	#define MDIO_MODE_MDC_MODE BIT(12)
	/* 0 = Clause 22, 1 = Clause 45 */
	#define MDIO_MODE_C45 BIT(8)
	#define MDIO_MODE_DIV_MASK GENMASK(7, 0)
	#define MDIO_MODE_DIV(x) FIELD_PREP(MDIO_MODE_DIV_MASK, (x) - 1)
	#define MDIO_MODE_DIV_1 0x0
	#define MDIO_MODE_DIV_2 0x1
	#define MDIO_MODE_DIV_4 0x3
	#define MDIO_MODE_DIV_8 0x7
	#define MDIO_MODE_DIV_16 0xf
	#define MDIO_MODE_DIV_32 0x1f
	#define MDIO_MODE_DIV_64 0x3f
	#define MDIO_MODE_DIV_128 0x7f
	#define MDIO_MODE_DIV_256 0xff
	#define MDIO_ADDR_REG 0x44
	#define MDIO_DATA_WRITE_REG 0x48
	#define MDIO_DATA_READ_REG 0x4c
	#define MDIO_CMD_REG 0x50
	#define MDIO_CMD_ACCESS_BUSY BIT(16)
	#define MDIO_CMD_ACCESS_START BIT(8)
	#define MDIO_CMD_ACCESS_CODE_READ 0
	#define MDIO_CMD_ACCESS_CODE_WRITE 1
	#define MDIO_CMD_ACCESS_CODE_C45_ADDR 0
	#define MDIO_CMD_ACCESS_CODE_C45_WRITE 1
	#define MDIO_CMD_ACCESS_CODE_C45_READ 2

	#define IPQ4019_MDIO_TIMEOUT 10000
	#define IPQ4019_MDIO_SLEEP 10

	/* MDIO clock source frequency is fixed to 100M */
	#define IPQ_MDIO_CLK_RATE 100000000

	#define IPQ_PHY_SET_DELAY_US 100000

	struct ipq4019_mdio_data {
	void __iomem *membase;
	void __iomem *eth_ldo_rdy;
	struct clk *mdio_clk;
	unsigned int mdc_rate;
	};

	static int ipq4019_mdio_wait_busy(struct mii_bus *bus)
	{
	struct ipq4019_mdio_data *priv = bus->priv;
	unsigned int busy;

	return readl_poll_timeout(priv->membase + MDIO_CMD_REG, busy,
	(busy & MDIO_CMD_ACCESS_BUSY) == 0,
	IPQ4019_MDIO_SLEEP, IPQ4019_MDIO_TIMEOUT);
	}

	static int ipq4019_mdio_read_c45(struct mii_bus *bus, int mii_id, int mmd,
	int reg)
	{
	struct ipq4019_mdio_data *priv = bus->priv;
	unsigned int data;
	unsigned int cmd;

	if (ipq4019_mdio_wait_busy(bus))
	return -ETIMEDOUT;

	data = readl(priv->membase + MDIO_MODE_REG);

	data \|= MDIO_MODE_C45;

	writel(data, priv->membase + MDIO_MODE_REG);

	/* issue the phy address and mmd */
	writel((mii_id << 8) \| mmd, priv->membase + MDIO_ADDR_REG);

	/* issue reg */
	writel(reg, priv->membase + MDIO_DATA_WRITE_REG);

	cmd = MDIO_CMD_ACCESS_START \| MDIO_CMD_ACCESS_CODE_C45_ADDR;

	/* issue read command */
	writel(cmd, priv->membase + MDIO_CMD_REG);

	/* Wait read complete */
	if (ipq4019_mdio_wait_busy(bus))
	return -ETIMEDOUT;

	cmd = MDIO_CMD_ACCESS_START \| MDIO_CMD_ACCESS_CODE_C45_READ;

	writel(cmd, priv->membase + MDIO_CMD_REG);

	if (ipq4019_mdio_wait_busy(bus))
	return -ETIMEDOUT;

	/* Read and return data */
	return readl(priv->membase + MDIO_DATA_READ_REG);
	}

	static int ipq4019_mdio_read_c22(struct mii_bus *bus, int mii_id, int regnum)
	{
	struct ipq4019_mdio_data *priv = bus->priv;
	unsigned int data;
	unsigned int cmd;

	if (ipq4019_mdio_wait_busy(bus))
	return -ETIMEDOUT;

	data = readl(priv->membase + MDIO_MODE_REG);

	data &= ~MDIO_MODE_C45;

	writel(data, priv->membase + MDIO_MODE_REG);

	/* issue the phy address and reg */
	writel((mii_id << 8) \| regnum, priv->membase + MDIO_ADDR_REG);

	cmd = MDIO_CMD_ACCESS_START \| MDIO_CMD_ACCESS_CODE_READ;

	/* issue read command */
	writel(cmd, priv->membase + MDIO_CMD_REG);

	/* Wait read complete */
	if (ipq4019_mdio_wait_busy(bus))
	return -ETIMEDOUT;

	/* Read and return data */
	return readl(priv->membase + MDIO_DATA_READ_REG);
	}

	static int ipq4019_mdio_write_c45(struct mii_bus *bus, int mii_id, int mmd,
	int reg, u16 value)
	{
	struct ipq4019_mdio_data *priv = bus->priv;
	unsigned int data;
	unsigned int cmd;

	if (ipq4019_mdio_wait_busy(bus))
	return -ETIMEDOUT;

	data = readl(priv->membase + MDIO_MODE_REG);

	data \|= MDIO_MODE_C45;

	writel(data, priv->membase + MDIO_MODE_REG);

	/* issue the phy address and mmd */
	writel((mii_id << 8) \| mmd, priv->membase + MDIO_ADDR_REG);

	/* issue reg */
	writel(reg, priv->membase + MDIO_DATA_WRITE_REG);

	cmd = MDIO_CMD_ACCESS_START \| MDIO_CMD_ACCESS_CODE_C45_ADDR;

	writel(cmd, priv->membase + MDIO_CMD_REG);

	if (ipq4019_mdio_wait_busy(bus))
	return -ETIMEDOUT;

	/* issue write data */
	writel(value, priv->membase + MDIO_DATA_WRITE_REG);

	cmd = MDIO_CMD_ACCESS_START \| MDIO_CMD_ACCESS_CODE_C45_WRITE;
	writel(cmd, priv->membase + MDIO_CMD_REG);

	/* Wait write complete */
	if (ipq4019_mdio_wait_busy(bus))
	return -ETIMEDOUT;

	return 0;
	}

	static int ipq4019_mdio_write_c22(struct mii_bus *bus, int mii_id, int regnum,
	u16 value)
	{
	struct ipq4019_mdio_data *priv = bus->priv;
	unsigned int data;
	unsigned int cmd;

	if (ipq4019_mdio_wait_busy(bus))
	return -ETIMEDOUT;

	/* Enter Clause 22 mode */
	data = readl(priv->membase + MDIO_MODE_REG);

	data &= ~MDIO_MODE_C45;

	writel(data, priv->membase + MDIO_MODE_REG);

	/* issue the phy address and reg */
	writel((mii_id << 8) \| regnum, priv->membase + MDIO_ADDR_REG);

	/* issue write data */
	writel(value, priv->membase + MDIO_DATA_WRITE_REG);

	/* issue write command */
	cmd = MDIO_CMD_ACCESS_START \| MDIO_CMD_ACCESS_CODE_WRITE;

	writel(cmd, priv->membase + MDIO_CMD_REG);

	/* Wait write complete */
	if (ipq4019_mdio_wait_busy(bus))
	return -ETIMEDOUT;

	return 0;
	}

	static int ipq4019_mdio_set_div(struct ipq4019_mdio_data *priv)
	{
	unsigned long ahb_rate;
	int div;
	u32 val;

	/* If we don't have a clock for AHB use the fixed value */
	ahb_rate = IPQ_MDIO_CLK_RATE;
	if (priv->mdio_clk)
	ahb_rate = clk_get_rate(priv->mdio_clk);

	/* MDC rate is ahb_rate/(MDIO_MODE_DIV + 1)
	* While supported, internal documentation doesn't
	* assure correct functionality of the MDIO bus
	* with divider of 1, 2 or 4.
	*/
	for (div = 8; div <= 256; div *= 2) {
	/* The requested rate is supported by the div */
	if (priv->mdc_rate == DIV_ROUND_UP(ahb_rate, div)) {
	val = readl(priv->membase + MDIO_MODE_REG);
	val &= ~MDIO_MODE_DIV_MASK;
	val \|= MDIO_MODE_DIV(div);
	writel(val, priv->membase + MDIO_MODE_REG);

	return 0;
	}
	}

	/* The requested rate is not supported */
	return -EINVAL;
	}

	static int ipq_mdio_reset(struct mii_bus *bus)
	{
	struct ipq4019_mdio_data *priv = bus->priv;
	u32 val;
	int ret;

	/* To indicate CMN_PLL that ethernet_ldo has been ready if platform resource 1
	* is specified in the device tree.
	*/
	if (priv->eth_ldo_rdy) {
	val = readl(priv->eth_ldo_rdy);
	val \|= BIT(0);
	writel(val, priv->eth_ldo_rdy);
	fsleep(IPQ_PHY_SET_DELAY_US);
	}

	/* Configure MDIO clock source frequency if clock is specified in the device tree */
	ret = clk_set_rate(priv->mdio_clk, IPQ_MDIO_CLK_RATE);
	if (ret)
	return ret;

	ret = clk_prepare_enable(priv->mdio_clk);
	if (ret)
	return ret;

	mdelay(10);

	/* Restore MDC rate */
	return ipq4019_mdio_set_div(priv);
	}

	static void ipq4019_mdio_select_mdc_rate(struct platform_device *pdev,
	struct ipq4019_mdio_data *priv)
	{
	unsigned long ahb_rate;
	int div;
	u32 val;

	/* MDC rate defined in DT, we don't have to decide a default value */
	if (!of_property_read_u32(pdev->dev.of_node, "clock-frequency",
	&priv->mdc_rate))
	return;

	/* If we don't have a clock for AHB use the fixed value */
	ahb_rate = IPQ_MDIO_CLK_RATE;
	if (priv->mdio_clk)
	ahb_rate = clk_get_rate(priv->mdio_clk);

	/* Check what is the current div set */
	val = readl(priv->membase + MDIO_MODE_REG);
	div = FIELD_GET(MDIO_MODE_DIV_MASK, val);

	/* div is not set to the default value of /256
	* Probably someone changed that (bootloader, other drivers)
	* Keep this and don't overwrite it.
	*/
	if (div != MDIO_MODE_DIV_256) {
	priv->mdc_rate = DIV_ROUND_UP(ahb_rate, div + 1);
	return;
	}

	/* If div is /256 assume nobody have set this value and
	* try to find one MDC rate that is close the 802.3 spec of
	* 2.5MHz
	*/
	for (div = 256; div >= 8; div /= 2) {
	/* Stop as soon as we found a divider that
	* reached the closest value to 2.5MHz
	*/
	if (DIV_ROUND_UP(ahb_rate, div) > 2500000)
	break;

	priv->mdc_rate = DIV_ROUND_UP(ahb_rate, div);
	}
	}

	static int ipq4019_mdio_probe(struct platform_device *pdev)
	{
	struct ipq4019_mdio_data *priv;
	struct mii_bus *bus;
	struct resource *res;
	int ret;

	bus = devm_mdiobus_alloc_size(&pdev->dev, sizeof(*priv));
	if (!bus)
	return -ENOMEM;

	priv = bus->priv;

	priv->membase = devm_platform_ioremap_resource(pdev, 0);
	if (IS_ERR(priv->membase))
	return PTR_ERR(priv->membase);

	priv->mdio_clk = devm_clk_get_optional(&pdev->dev, "gcc_mdio_ahb_clk");
	if (IS_ERR(priv->mdio_clk))
	return PTR_ERR(priv->mdio_clk);

	ipq4019_mdio_select_mdc_rate(pdev, priv);
	ret = ipq4019_mdio_set_div(priv);
	if (ret)
	return ret;

	/* The platform resource is provided on the chipset IPQ5018 */
	/* This resource is optional */
	res = platform_get_resource(pdev, IORESOURCE_MEM, 1);
	if (res)
	priv->eth_ldo_rdy = devm_ioremap_resource(&pdev->dev, res);

	bus->name = "ipq4019_mdio";
	bus->read = ipq4019_mdio_read_c22;
	bus->write = ipq4019_mdio_write_c22;
	bus->read_c45 = ipq4019_mdio_read_c45;
	bus->write_c45 = ipq4019_mdio_write_c45;
	bus->reset = ipq_mdio_reset;
	bus->parent = &pdev->dev;
	snprintf(bus->id, MII_BUS_ID_SIZE, "%s%d", pdev->name, pdev->id);

	ret = of_mdiobus_register(bus, pdev->dev.of_node);
	if (ret) {
	dev_err(&pdev->dev, "Cannot register MDIO bus!\n");
	return ret;
	}

	platform_set_drvdata(pdev, bus);

	return 0;
	}

	static void ipq4019_mdio_remove(struct platform_device *pdev)
	{
	struct mii_bus *bus = platform_get_drvdata(pdev);

	mdiobus_unregister(bus);
	}

	static const struct of_device_id ipq4019_mdio_dt_ids[] = {
	{ .compatible = "qcom,ipq4019-mdio" },
	{ .compatible = "qcom,ipq5018-mdio" },
	{ }
	};
	MODULE_DEVICE_TABLE(of, ipq4019_mdio_dt_ids);

	static struct platform_driver ipq4019_mdio_driver = {
	.probe = ipq4019_mdio_probe,
	.remove_new = ipq4019_mdio_remove,
	.driver = {
	.name = "ipq4019-mdio",
	.of_match_table = ipq4019_mdio_dt_ids,
	},
	};

	module_platform_driver(ipq4019_mdio_driver);

	MODULE_DESCRIPTION("ipq4019 MDIO interface driver");
	MODULE_AUTHOR("Qualcomm Atheros");
	MODULE_LICENSE("Dual BSD/GPL");