/*
   * drivers/uio/uio_pdrv_genirq.c
   *
   * Userspace I/O platform driver with generic IRQ handling code.
   *
   * Copyright (C) 2008 Magnus Damm
   *
   * Based on uio_pdrv.c by Uwe Kleine-Koenig,
   * Copyright (C) 2008 by Digi International Inc.
   * All rights reserved.
   *
   * This program is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License version 2 as published by
   * the Free Software Foundation.
   */
  
  #include <linux/platform_device.h>
  #include <linux/uio_driver.h>
  #include <linux/spinlock.h>
  #include <linux/bitops.h>

  #include <linux/module.h>

  #include <linux/interrupt.h>
  #include <linux/stringify.h>

  #include <linux/pm_runtime.h>

  #include <linux/slab.h>

  #include <linux/of.h>
  #include <linux/of_platform.h>
  #include <linux/of_address.h>

  #define DRIVER_NAME "uio_pdrv_genirq"
  
  struct uio_pdrv_genirq_platdata {
  	struct uio_info *uioinfo;
  	spinlock_t lock;
  	unsigned long flags;

  	struct platform_device *pdev;

  };

  static int uio_pdrv_genirq_open(struct uio_info *info, struct inode *inode)
  {
  	struct uio_pdrv_genirq_platdata *priv = info->priv;
  
  	/* Wait until the Runtime PM code has woken up the device */
  	pm_runtime_get_sync(&priv->pdev->dev);
  	return 0;
  }
  
  static int uio_pdrv_genirq_release(struct uio_info *info, struct inode *inode)
  {
  	struct uio_pdrv_genirq_platdata *priv = info->priv;
  
  	/* Tell the Runtime PM code that the device has become idle */
  	pm_runtime_put_sync(&priv->pdev->dev);
  	return 0;
  }

  static irqreturn_t uio_pdrv_genirq_handler(int irq, struct uio_info *dev_info)
  {
  	struct uio_pdrv_genirq_platdata *priv = dev_info->priv;
  
  	/* Just disable the interrupt in the interrupt controller, and
  	 * remember the state so we can allow user space to enable it later.
  	 */
  
  	if (!test_and_set_bit(0, &priv->flags))
  		disable_irq_nosync(irq);
  
  	return IRQ_HANDLED;
  }
  
  static int uio_pdrv_genirq_irqcontrol(struct uio_info *dev_info, s32 irq_on)
  {
  	struct uio_pdrv_genirq_platdata *priv = dev_info->priv;
  	unsigned long flags;
  
  	/* Allow user space to enable and disable the interrupt
  	 * in the interrupt controller, but keep track of the
  	 * state to prevent per-irq depth damage.
  	 *
  	 * Serialize this operation to support multiple tasks.
  	 */
  
  	spin_lock_irqsave(&priv->lock, flags);
  	if (irq_on) {
  		if (test_and_clear_bit(0, &priv->flags))
  			enable_irq(dev_info->irq);
  	} else {
  		if (!test_and_set_bit(0, &priv->flags))
  			disable_irq(dev_info->irq);
  	}
  	spin_unlock_irqrestore(&priv->lock, flags);
  
  	return 0;
  }
  
  static int uio_pdrv_genirq_probe(struct platform_device *pdev)
  {
  	struct uio_info *uioinfo = pdev->dev.platform_data;
  	struct uio_pdrv_genirq_platdata *priv;
  	struct uio_mem *uiomem;
  	int ret = -EINVAL;
  	int i;

  	if (!uioinfo) {
  		int irq;
  
  		/* alloc uioinfo for one device */
  		uioinfo = kzalloc(sizeof(*uioinfo), GFP_KERNEL);
  		if (!uioinfo) {
  			ret = -ENOMEM;
  			dev_err(&pdev->dev, "unable to kmalloc
  ");
  			goto bad2;
  		}
  		uioinfo->name = pdev->dev.of_node->name;
  		uioinfo->version = "devicetree";
  
  		/* Multiple IRQs are not supported */
  		irq = platform_get_irq(pdev, 0);
  		if (irq == -ENXIO)
  			uioinfo->irq = UIO_IRQ_NONE;
  		else
  			uioinfo->irq = irq;
  	}

  	if (!uioinfo || !uioinfo->name || !uioinfo->version) {
  		dev_err(&pdev->dev, "missing platform_data
  ");
  		goto bad0;
  	}

  	if (uioinfo->handler || uioinfo->irqcontrol ||
  	    uioinfo->irq_flags & IRQF_SHARED) {

  		dev_err(&pdev->dev, "interrupt configuration error
  ");
  		goto bad0;
  	}
  
  	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
  	if (!priv) {
  		ret = -ENOMEM;
  		dev_err(&pdev->dev, "unable to kmalloc
  ");
  		goto bad0;
  	}
  
  	priv->uioinfo = uioinfo;
  	spin_lock_init(&priv->lock);
  	priv->flags = 0; /* interrupt is enabled to begin with */

  	priv->pdev = pdev;

  
  	uiomem = &uioinfo->mem[0];
  
  	for (i = 0; i < pdev->num_resources; ++i) {
  		struct resource *r = &pdev->resource[i];
  
  		if (r->flags != IORESOURCE_MEM)
  			continue;
  
  		if (uiomem >= &uioinfo->mem[MAX_UIO_MAPS]) {
  			dev_warn(&pdev->dev, "device has more than "
  					__stringify(MAX_UIO_MAPS)
  					" I/O memory resources.
  ");
  			break;
  		}
  
  		uiomem->memtype = UIO_MEM_PHYS;
  		uiomem->addr = r->start;

  		uiomem->size = resource_size(r);

  		++uiomem;
  	}
  
  	while (uiomem < &uioinfo->mem[MAX_UIO_MAPS]) {
  		uiomem->size = 0;
  		++uiomem;
  	}
  
  	/* This driver requires no hardware specific kernel code to handle
  	 * interrupts. Instead, the interrupt handler simply disables the
  	 * interrupt in the interrupt controller. User space is responsible
  	 * for performing hardware specific acknowledge and re-enabling of
  	 * the interrupt in the interrupt controller.
  	 *
  	 * Interrupt sharing is not supported.
  	 */

  	uioinfo->handler = uio_pdrv_genirq_handler;
  	uioinfo->irqcontrol = uio_pdrv_genirq_irqcontrol;

  	uioinfo->open = uio_pdrv_genirq_open;
  	uioinfo->release = uio_pdrv_genirq_release;

  	uioinfo->priv = priv;

  	/* Enable Runtime PM for this device:
  	 * The device starts in suspended state to allow the hardware to be
  	 * turned off by default. The Runtime PM bus code should power on the
  	 * hardware and enable clocks at open().
  	 */
  	pm_runtime_enable(&pdev->dev);

  	ret = uio_register_device(&pdev->dev, priv->uioinfo);
  	if (ret) {
  		dev_err(&pdev->dev, "unable to register uio device
  ");
  		goto bad1;
  	}
  
  	platform_set_drvdata(pdev, priv);
  	return 0;
   bad1:
  	kfree(priv);

  	pm_runtime_disable(&pdev->dev);

   bad0:

  	/* kfree uioinfo for OF */
  	if (pdev->dev.of_node)
  		kfree(uioinfo);
   bad2:

  	return ret;
  }
  
  static int uio_pdrv_genirq_remove(struct platform_device *pdev)
  {
  	struct uio_pdrv_genirq_platdata *priv = platform_get_drvdata(pdev);
  
  	uio_unregister_device(priv->uioinfo);

  	pm_runtime_disable(&pdev->dev);

  
  	priv->uioinfo->handler = NULL;
  	priv->uioinfo->irqcontrol = NULL;

  	/* kfree uioinfo for OF */
  	if (pdev->dev.of_node)
  		kfree(priv->uioinfo);

  	kfree(priv);
  	return 0;
  }

  static int uio_pdrv_genirq_runtime_nop(struct device *dev)
  {
  	/* Runtime PM callback shared between ->runtime_suspend()
  	 * and ->runtime_resume(). Simply returns success.
  	 *
  	 * In this driver pm_runtime_get_sync() and pm_runtime_put_sync()
  	 * are used at open() and release() time. This allows the
  	 * Runtime PM code to turn off power to the device while the
  	 * device is unused, ie before open() and after release().
  	 *
  	 * This Runtime PM callback does not need to save or restore
  	 * any registers since user space is responsbile for hardware
  	 * register reinitialization after open().
  	 */
  	return 0;
  }

  static const struct dev_pm_ops uio_pdrv_genirq_dev_pm_ops = {

  	.runtime_suspend = uio_pdrv_genirq_runtime_nop,
  	.runtime_resume = uio_pdrv_genirq_runtime_nop,
  };

  #ifdef CONFIG_OF

  static const struct of_device_id uio_of_genirq_match[] = {

  	{ /* empty for now */ },
  };
  MODULE_DEVICE_TABLE(of, uio_of_genirq_match);
  #else
  # define uio_of_genirq_match NULL
  #endif

  static struct platform_driver uio_pdrv_genirq = {
  	.probe = uio_pdrv_genirq_probe,
  	.remove = uio_pdrv_genirq_remove,
  	.driver = {
  		.name = DRIVER_NAME,
  		.owner = THIS_MODULE,

  		.pm = &uio_pdrv_genirq_dev_pm_ops,

  		.of_match_table = uio_of_genirq_match,

  	},
  };

  module_platform_driver(uio_pdrv_genirq);

  
  MODULE_AUTHOR("Magnus Damm");
  MODULE_DESCRIPTION("Userspace I/O platform driver with generic IRQ handling");
  MODULE_LICENSE("GPL v2");
  MODULE_ALIAS("platform:" DRIVER_NAME);