atmel-ssc.c

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/*
 * Atmel SSC driver
 *
 * Copyright (C) 2007 Atmel Corporation
 *
 * 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/list.h>
#include <linux/clk.h>
#include <linux/err.h>
#include <linux/io.h>
#include <linux/spinlock.h>
#include <linux/atmel-ssc.h>
#include <linux/slab.h>
#include <linux/module.h>

/* Serialize access to ssc_list and user count */
static DEFINE_SPINLOCK(user_lock);
static LIST_HEAD(ssc_list);

struct ssc_device *ssc_request(unsigned int ssc_num)
{
    int ssc_valid = 0;
    struct ssc_device *ssc;

    spin_lock(&user_lock);
    list_for_each_entry(ssc, &ssc_list, list) {
        if (ssc->pdev->id == ssc_num) {
            ssc_valid = 1;
            break;
        }
    }

    if (!ssc_valid) {
        spin_unlock(&user_lock);
        pr_err("ssc: ssc%d platform device is missing\n", ssc_num);
        return ERR_PTR(-ENODEV);
    }

    if (ssc->user) {
        spin_unlock(&user_lock);
        dev_dbg(&ssc->pdev->dev, "module busy\n");
        return ERR_PTR(-EBUSY);
    }
    ssc->user++;
    spin_unlock(&user_lock);

    clk_enable(ssc->clk);

    return ssc;
}
EXPORT_SYMBOL(ssc_request);

void ssc_free(struct ssc_device *ssc)
{
    spin_lock(&user_lock);
    if (ssc->user) {
        ssc->user--;
        clk_disable(ssc->clk);
    } else {
        dev_dbg(&ssc->pdev->dev, "device already free\n");
    }
    spin_unlock(&user_lock);
}
EXPORT_SYMBOL(ssc_free);

static int __init ssc_probe(struct platform_device *pdev)
{
    int retval = 0;
    struct resource *regs;
    struct ssc_device *ssc;

    ssc = kzalloc(sizeof(struct ssc_device), GFP_KERNEL);
    if (!ssc) {
        dev_dbg(&pdev->dev, "out of memory\n");
        retval = -ENOMEM;
        goto out;
    }

    regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
    if (!regs) {
        dev_dbg(&pdev->dev, "no mmio resource defined\n");
        retval = -ENXIO;
        goto out_free;
    }

    ssc->clk = clk_get(&pdev->dev, "pclk");
    if (IS_ERR(ssc->clk)) {
        dev_dbg(&pdev->dev, "no pclk clock defined\n");
        retval = -ENXIO;
        goto out_free;
    }

    ssc->pdev = pdev;
    ssc->regs = ioremap(regs->start, resource_size(regs));
    if (!ssc->regs) {
        dev_dbg(&pdev->dev, "ioremap failed\n");
        retval = -EINVAL;
        goto out_clk;
    }

    /* disable all interrupts */
    clk_enable(ssc->clk);
    ssc_writel(ssc->regs, IDR, ~0UL);
    ssc_readl(ssc->regs, SR);
    clk_disable(ssc->clk);

    ssc->irq = platform_get_irq(pdev, 0);
    if (!ssc->irq) {
        dev_dbg(&pdev->dev, "could not get irq\n");
        retval = -ENXIO;
        goto out_unmap;
    }

    spin_lock(&user_lock);
    list_add_tail(&ssc->list, &ssc_list);
    spin_unlock(&user_lock);

    platform_set_drvdata(pdev, ssc);

    dev_info(&pdev->dev, "Atmel SSC device at 0x%p (irq %d)\n",
            ssc->regs, ssc->irq);

    goto out;

out_unmap:
    iounmap(ssc->regs);
out_clk:
    clk_put(ssc->clk);
out_free:
    kfree(ssc);
out:
    return retval;
}

static int __devexit ssc_remove(struct platform_device *pdev)
{
    struct ssc_device *ssc = platform_get_drvdata(pdev);

    spin_lock(&user_lock);
    iounmap(ssc->regs);
    clk_put(ssc->clk);
    list_del(&ssc->list);
    kfree(ssc);
    spin_unlock(&user_lock);

    return 0;
}

static struct platform_driver ssc_driver = {
    .remove     = __devexit_p(ssc_remove),
    .driver     = {
        .name       = "ssc",
        .owner      = THIS_MODULE,
    },
};

static int __init ssc_init(void)
{
    return platform_driver_probe(&ssc_driver, ssc_probe);
}
module_init(ssc_init);

static void __exit ssc_exit(void)
{
    platform_driver_unregister(&ssc_driver);
}
module_exit(ssc_exit);

MODULE_AUTHOR("Hans-Christian Egtvedt <[email protected]>");
MODULE_DESCRIPTION("SSC driver for Atmel AVR32 and AT91");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:ssc");