uio_pdrv_genirq.c

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/*
 * 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);