// SPDX-License-Identifier: GPL-2.0
/*
 * OMAP hardware spinlock driver
 *
 * Copyright (C) 2010-2021 Texas Instruments Incorporated - https://www.ti.com
 *
 * Contact: Simon Que <sque@ti.com>
 *          Hari Kanigeri <h-kanigeri2@ti.com>
 *          Ohad Ben-Cohen <ohad@wizery.com>
 *          Suman Anna <s-anna@ti.com>
 */

#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/of.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 omap_hwspinlock_probe(struct platform_device *pdev)
{
        struct hwspinlock_device *bank;
        void __iomem *io_base;
        int num_locks, i, ret;
        /* Only a single hwspinlock block device is supported */
        int base_id = 0;

        io_base = devm_platform_ioremap_resource(pdev, 0);
        if (IS_ERR(io_base))
                return PTR_ERR(io_base);

        /*
         * make sure the module is enabled and clocked before reading
         * the module SYSSTATUS register
         */
        ret = devm_pm_runtime_enable(&pdev->dev);
        if (ret)
                return ret;
        ret = pm_runtime_resume_and_get(&pdev->dev);
        if (ret < 0)
                return ret;

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

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

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

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

        bank = devm_kzalloc(&pdev->dev, struct_size(bank, lock, num_locks),
                            GFP_KERNEL);
        if (!bank)
                return -ENOMEM;

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

        return devm_hwspin_lock_register(&pdev->dev, bank, &omap_hwspinlock_ops,
                                                base_id, num_locks);
}

static const struct of_device_id omap_hwspinlock_of_match[] = {
        { .compatible = "ti,omap4-hwspinlock", },
        { .compatible = "ti,am64-hwspinlock", },
        { .compatible = "ti,am654-hwspinlock", },
        { /* end */ },
};
MODULE_DEVICE_TABLE(of, omap_hwspinlock_of_match);

static struct platform_driver omap_hwspinlock_driver = {
        .probe          = omap_hwspinlock_probe,
        .driver         = {
                .name   = "omap_hwspinlock",
                .of_match_table = omap_hwspinlock_of_match,
        },
};

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 <sque@ti.com>");
MODULE_AUTHOR("Hari Kanigeri <h-kanigeri2@ti.com>");
MODULE_AUTHOR("Ohad Ben-Cohen <ohad@wizery.com>");