/*
   * 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
  ");
  	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
  ");
  		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 i, ret;
  
  	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
  	if (!r) {
  		dev_err(&pdev->dev, "No SMI register address given
  ");
  		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;
  
  	bus->irq = devm_kmalloc_array(&pdev->dev, PHY_MAX_ADDR, sizeof(int),
  				      GFP_KERNEL);
  	if (!bus->irq)
  		return -ENOMEM;
  
  	for (i = 0; i < PHY_MAX_ADDR; i++)
  		bus->irq[i] = PHY_POLL;
  
  	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
  ");
  		ret = -ENODEV;
  		goto out_mdio;
  	}
  
  	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)
  ", 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");