/*
 * 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\n");
                        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\n");
                goto bad0;
        }

        if (uioinfo->handler || uioinfo->irqcontrol ||
            uioinfo->irq_flags & IRQF_SHARED) {
                dev_err(&pdev->dev, "interrupt configuration error\n");
                goto bad0;
        }

        priv = kzalloc(sizeof(*priv), GFP_KERNEL);
        if (!priv) {
                ret = -ENOMEM;
                dev_err(&pdev->dev, "unable to kmalloc\n");
                goto bad0;
        }

        priv->uioinfo = uioinfo;
        spin_lock_init(&priv->lock);
        priv->flags = 0; /* interrupt is enabled to begin with */
        priv->pdev = pdev;

        if (!uioinfo->irq) {
                ret = platform_get_irq(pdev, 0);
                if (ret < 0) {
                        dev_err(&pdev->dev, "failed to get IRQ\n");
                        goto bad0;
                }
                uioinfo->irq = ret;
        }
        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.\n");
                        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\n");
                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);