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/*
 * Driver for the MDIO interface of Marvell network interfaces.
 *
 * Since the MDIO interface of Marvell network interfaces is shared
 * between all network interfaces, having a single driver allows to
 * handle concurrent accesses properly (you may have four Ethernet
 * ports, but they in fact share the same SMI interface to access
 * the MDIO bus). This driver is currently used by the mvneta and
 * mv643xx_eth drivers.
 *
 * Copyright (C) 2012 Marvell
 *
 * Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
 *
 * This file is licensed under the terms of the GNU General Public
 * License version 2. This program is licensed "as is" without any
 * warranty of any kind, whether express or implied.
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/phy.h>
#include <linux/interrupt.h>
#include <linux/platform_device.h>
#include <linux/delay.h>
#include <linux/io.h>
#include <linux/clk.h>
#include <linux/of_mdio.h>
#include <linux/sched.h>
#include <linux/wait.h>

#define MVMDIO_SMI_DATA_SHIFT              0
#define MVMDIO_SMI_PHY_ADDR_SHIFT          16
#define MVMDIO_SMI_PHY_REG_SHIFT           21
#define MVMDIO_SMI_READ_OPERATION          BIT(26)
#define MVMDIO_SMI_WRITE_OPERATION         0
#define MVMDIO_SMI_READ_VALID              BIT(27)
#define MVMDIO_SMI_BUSY                    BIT(28)
#define MVMDIO_ERR_INT_CAUSE		   0x007C
#define  MVMDIO_ERR_INT_SMI_DONE	   0x00000010
#define MVMDIO_ERR_INT_MASK		   0x0080

/*
 * SMI Timeout measurements:
 * - Kirkwood 88F6281 (Globalscale Dreamplug): 45us to 95us (Interrupt)
 * - Armada 370       (Globalscale Mirabox):   41us to 43us (Polled)
 */
#define MVMDIO_SMI_TIMEOUT		   1000 /* 1000us = 1ms */
#define MVMDIO_SMI_POLL_INTERVAL_MIN	   45
#define MVMDIO_SMI_POLL_INTERVAL_MAX	   55

struct orion_mdio_dev {
	struct mutex lock;
	void __iomem *regs;
	struct clk *clk;
	/*
	 * If we have access to the error interrupt pin (which is
	 * somewhat misnamed as it not only reflects internal errors
	 * but also reflects SMI completion), use that to wait for
	 * SMI access completion instead of polling the SMI busy bit.
	 */
	int err_interrupt;
	wait_queue_head_t smi_busy_wait;
};

static int orion_mdio_smi_is_done(struct orion_mdio_dev *dev)
{
	return !(readl(dev->regs) & MVMDIO_SMI_BUSY);
}

/* Wait for the SMI unit to be ready for another operation
 */
static int orion_mdio_wait_ready(struct mii_bus *bus)
{
	struct orion_mdio_dev *dev = bus->priv;
	unsigned long timeout = usecs_to_jiffies(MVMDIO_SMI_TIMEOUT);
	unsigned long end = jiffies + timeout;
	int timedout = 0;

	while (1) {
	        if (orion_mdio_smi_is_done(dev))
			return 0;
	        else if (timedout)
			break;

	        if (dev->err_interrupt <= 0) {
			usleep_range(MVMDIO_SMI_POLL_INTERVAL_MIN,
				     MVMDIO_SMI_POLL_INTERVAL_MAX);

			if (time_is_before_jiffies(end))
				++timedout;
	        } else {
			/* wait_event_timeout does not guarantee a delay of at
			 * least one whole jiffie, so timeout must be no less
			 * than two.
			 */
			if (timeout < 2)
				timeout = 2;
			wait_event_timeout(dev->smi_busy_wait,
				           orion_mdio_smi_is_done(dev),
				           timeout);

			++timedout;
	        }
	}

	dev_err(bus->parent, "Timeout: SMI busy for too long\n");
	return  -ETIMEDOUT;
}

static int orion_mdio_read(struct mii_bus *bus, int mii_id,
			   int regnum)
{
	struct orion_mdio_dev *dev = bus->priv;
	u32 val;
	int ret;

	mutex_lock(&dev->lock);

	ret = orion_mdio_wait_ready(bus);
	if (ret < 0)
		goto out;

	writel(((mii_id << MVMDIO_SMI_PHY_ADDR_SHIFT) |
		(regnum << MVMDIO_SMI_PHY_REG_SHIFT)  |
		MVMDIO_SMI_READ_OPERATION),
	       dev->regs);

	ret = orion_mdio_wait_ready(bus);
	if (ret < 0)
		goto out;

	val = readl(dev->regs);
	if (!(val & MVMDIO_SMI_READ_VALID)) {
		dev_err(bus->parent, "SMI bus read not valid\n");
		ret = -ENODEV;
		goto out;
	}

	ret = val & 0xFFFF;
out:
	mutex_unlock(&dev->lock);
	return ret;
}

static int orion_mdio_write(struct mii_bus *bus, int mii_id,
			    int regnum, u16 value)
{
	struct orion_mdio_dev *dev = bus->priv;
	int ret;

	mutex_lock(&dev->lock);

	ret = orion_mdio_wait_ready(bus);
	if (ret < 0)
		goto out;

	writel(((mii_id << MVMDIO_SMI_PHY_ADDR_SHIFT) |
		(regnum << MVMDIO_SMI_PHY_REG_SHIFT)  |
		MVMDIO_SMI_WRITE_OPERATION            |
		(value << MVMDIO_SMI_DATA_SHIFT)),
	       dev->regs);

out:
	mutex_unlock(&dev->lock);
	return ret;
}

static irqreturn_t orion_mdio_err_irq(int irq, void *dev_id)
{
	struct orion_mdio_dev *dev = dev_id;

	if (readl(dev->regs + MVMDIO_ERR_INT_CAUSE) &
			MVMDIO_ERR_INT_SMI_DONE) {
		writel(~MVMDIO_ERR_INT_SMI_DONE,
				dev->regs + MVMDIO_ERR_INT_CAUSE);
		wake_up(&dev->smi_busy_wait);
		return IRQ_HANDLED;
	}

	return IRQ_NONE;
}

static int orion_mdio_probe(struct platform_device *pdev)
{
	struct resource *r;
	struct mii_bus *bus;
	struct orion_mdio_dev *dev;
	int ret;

	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	if (!r) {
		dev_err(&pdev->dev, "No SMI register address given\n");
		return -ENODEV;
	}

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

	bus->name = "orion_mdio_bus";
	bus->read = orion_mdio_read;
	bus->write = orion_mdio_write;
	snprintf(bus->id, MII_BUS_ID_SIZE, "%s-mii",
		 dev_name(&pdev->dev));
	bus->parent = &pdev->dev;

	dev = bus->priv;
	dev->regs = devm_ioremap(&pdev->dev, r->start, resource_size(r));
	if (!dev->regs) {
		dev_err(&pdev->dev, "Unable to remap SMI register\n");
		return -ENODEV;
	}

	init_waitqueue_head(&dev->smi_busy_wait);

	dev->clk = devm_clk_get(&pdev->dev, NULL);
	if (!IS_ERR(dev->clk))
		clk_prepare_enable(dev->clk);

	dev->err_interrupt = platform_get_irq(pdev, 0);
	if (dev->err_interrupt > 0) {
		ret = devm_request_irq(&pdev->dev, dev->err_interrupt,
					orion_mdio_err_irq,
					IRQF_SHARED, pdev->name, dev);
		if (ret)
			goto out_mdio;

		writel(MVMDIO_ERR_INT_SMI_DONE,
			dev->regs + MVMDIO_ERR_INT_MASK);

	} else if (dev->err_interrupt == -EPROBE_DEFER) {
		return -EPROBE_DEFER;
	}

	mutex_init(&dev->lock);

	if (pdev->dev.of_node)
		ret = of_mdiobus_register(bus, pdev->dev.of_node);
	else
		ret = mdiobus_register(bus);
	if (ret < 0) {
		dev_err(&pdev->dev, "Cannot register MDIO bus (%d)\n", ret);
		goto out_mdio;
	}

	platform_set_drvdata(pdev, bus);

	return 0;

out_mdio:
	if (!IS_ERR(dev->clk))
		clk_disable_unprepare(dev->clk);
	return ret;
}

static int orion_mdio_remove(struct platform_device *pdev)
{
	struct mii_bus *bus = platform_get_drvdata(pdev);
	struct orion_mdio_dev *dev = bus->priv;

	writel(0, dev->regs + MVMDIO_ERR_INT_MASK);
	mdiobus_unregister(bus);
	if (!IS_ERR(dev->clk))
		clk_disable_unprepare(dev->clk);

	return 0;
}

static const struct of_device_id orion_mdio_match[] = {
	{ .compatible = "marvell,orion-mdio" },
	{ }
};
MODULE_DEVICE_TABLE(of, orion_mdio_match);

static struct platform_driver orion_mdio_driver = {
	.probe = orion_mdio_probe,
	.remove = orion_mdio_remove,
	.driver = {
		.name = "orion-mdio",
		.of_match_table = orion_mdio_match,
	},
};

module_platform_driver(orion_mdio_driver);

MODULE_DESCRIPTION("Marvell MDIO interface driver");
MODULE_AUTHOR("Thomas Petazzoni <thomas.petazzoni@free-electrons.com>");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:orion-mdio");