omap_hwspinlock.c

Go to the documentation of this file.

/*
 * OMAP hardware spinlock driver
 *
 * Copyright (C) 2010 Texas Instruments Incorporated - http://www.ti.com
 *
 * Contact: Simon Que <[email protected]>
 *          Hari Kanigeri <[email protected]>
 *          Ohad Ben-Cohen <[email protected]>
 *
 * 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.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/delay.h>
#include <linux/io.h>
#include <linux/bitops.h>
#include <linux/pm_runtime.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/hwspinlock.h>
#include <linux/platform_device.h>

#include "hwspinlock_internal.h"

/* Spinlock register offsets */
#define SYSSTATUS_OFFSET        0x0014
#define LOCK_BASE_OFFSET        0x0800

#define SPINLOCK_NUMLOCKS_BIT_OFFSET    (24)

/* Possible values of SPINLOCK_LOCK_REG */
#define SPINLOCK_NOTTAKEN       (0) /* free */
#define SPINLOCK_TAKEN          (1) /* locked */

static int omap_hwspinlock_trylock(struct hwspinlock *lock)
{
    void __iomem *lock_addr = lock->priv;

    /* attempt to acquire the lock by reading its value */
    return (SPINLOCK_NOTTAKEN == readl(lock_addr));
}

static void omap_hwspinlock_unlock(struct hwspinlock *lock)
{
    void __iomem *lock_addr = lock->priv;

    /* release the lock by writing 0 to it */
    writel(SPINLOCK_NOTTAKEN, lock_addr);
}

/*
 * relax the OMAP interconnect while spinning on it.
 *
 * The specs recommended that the retry delay time will be
 * just over half of the time that a requester would be
 * expected to hold the lock.
 *
 * The number below is taken from an hardware specs example,
 * obviously it is somewhat arbitrary.
 */
static void omap_hwspinlock_relax(struct hwspinlock *lock)
{
    ndelay(50);
}

static const struct hwspinlock_ops omap_hwspinlock_ops = {
    .trylock = omap_hwspinlock_trylock,
    .unlock = omap_hwspinlock_unlock,
    .relax = omap_hwspinlock_relax,
};

static int __devinit omap_hwspinlock_probe(struct platform_device *pdev)
{
    struct hwspinlock_pdata *pdata = pdev->dev.platform_data;
    struct hwspinlock_device *bank;
    struct hwspinlock *hwlock;
    struct resource *res;
    void __iomem *io_base;
    int num_locks, i, ret;

    if (!pdata)
        return -ENODEV;

    res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
    if (!res)
        return -ENODEV;

    io_base = ioremap(res->start, resource_size(res));
    if (!io_base)
        return -ENOMEM;

    /* Determine number of locks */
    i = readl(io_base + SYSSTATUS_OFFSET);
    i >>= SPINLOCK_NUMLOCKS_BIT_OFFSET;

    /* one of the four lsb's must be set, and nothing else */
    if (hweight_long(i & 0xf) != 1 || i > 8) {
        ret = -EINVAL;
        goto iounmap_base;
    }

    num_locks = i * 32; /* actual number of locks in this device */

    bank = kzalloc(sizeof(*bank) + num_locks * sizeof(*hwlock), GFP_KERNEL);
    if (!bank) {
        ret = -ENOMEM;
        goto iounmap_base;
    }

    platform_set_drvdata(pdev, bank);

    for (i = 0, hwlock = &bank->lock[0]; i < num_locks; i++, hwlock++)
        hwlock->priv = io_base + LOCK_BASE_OFFSET + sizeof(u32) * i;

    /*
     * runtime PM will make sure the clock of this module is
     * enabled iff at least one lock is requested
     */
    pm_runtime_enable(&pdev->dev);

    ret = hwspin_lock_register(bank, &pdev->dev, &omap_hwspinlock_ops,
                        pdata->base_id, num_locks);
    if (ret)
        goto reg_fail;

    return 0;

reg_fail:
    pm_runtime_disable(&pdev->dev);
    kfree(bank);
iounmap_base:
    iounmap(io_base);
    return ret;
}

static int __devexit omap_hwspinlock_remove(struct platform_device *pdev)
{
    struct hwspinlock_device *bank = platform_get_drvdata(pdev);
    void __iomem *io_base = bank->lock[0].priv - LOCK_BASE_OFFSET;
    int ret;

    ret = hwspin_lock_unregister(bank);
    if (ret) {
        dev_err(&pdev->dev, "%s failed: %d\n", __func__, ret);
        return ret;
    }

    pm_runtime_disable(&pdev->dev);
    iounmap(io_base);
    kfree(bank);

    return 0;
}

static struct platform_driver omap_hwspinlock_driver = {
    .probe      = omap_hwspinlock_probe,
    .remove     = __devexit_p(omap_hwspinlock_remove),
    .driver     = {
        .name   = "omap_hwspinlock",
        .owner  = THIS_MODULE,
    },
};

static int __init omap_hwspinlock_init(void)
{
    return platform_driver_register(&omap_hwspinlock_driver);
}
/* board init code might need to reserve hwspinlocks for predefined purposes */
postcore_initcall(omap_hwspinlock_init);

static void __exit omap_hwspinlock_exit(void)
{
    platform_driver_unregister(&omap_hwspinlock_driver);
}
module_exit(omap_hwspinlock_exit);

MODULE_LICENSE("GPL v2");
MODULE_DESCRIPTION("Hardware spinlock driver for OMAP");
MODULE_AUTHOR("Simon Que <[email protected]>");
MODULE_AUTHOR("Hari Kanigeri <[email protected]>");
MODULE_AUTHOR("Ohad Ben-Cohen <[email protected]>");