/*
 * omap-rng.c - RNG driver for TI OMAP CPU family
 *
 * Author: Deepak Saxena <dsaxena@plexity.net>
 *
 * Copyright 2005 (c) MontaVista Software, Inc.
 *
 * Mostly based on original driver:
 *
 * Copyright (C) 2005 Nokia Corporation
 * Author: Juha Yrjölä <juha.yrjola@nokia.com>
 *
 * This file is licensed under  the terms of the GNU General Public
 * License version 2. This program is licensed "as is" without any
 * warranty of any kind, whether express or implied.
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/random.h>
#include <linux/clk.h>
#include <linux/err.h>
#include <linux/platform_device.h>
#include <linux/hw_random.h>
#include <linux/delay.h>

#include <asm/io.h>

#define RNG_OUT_REG             0x00            /* Output register */
#define RNG_STAT_REG            0x04            /* Status register
                                                        [0] = STAT_BUSY */
#define RNG_ALARM_REG           0x24            /* Alarm register
                                                        [7:0] = ALARM_COUNTER */
#define RNG_CONFIG_REG          0x28            /* Configuration register
                                                        [11:6] = RESET_COUNT
                                                        [5:3]  = RING2_DELAY
                                                        [2:0]  = RING1_DELAY */
#define RNG_REV_REG             0x3c            /* Revision register
                                                        [7:0] = REV_NB */
#define RNG_MASK_REG            0x40            /* Mask and reset register
                                                        [2] = IT_EN
                                                        [1] = SOFTRESET
                                                        [0] = AUTOIDLE */
#define RNG_SYSSTATUS           0x44            /* System status
                                                        [0] = RESETDONE */

static void __iomem *rng_base;
static struct clk *rng_ick;
static struct platform_device *rng_dev;

static inline u32 omap_rng_read_reg(int reg)
{
        return __raw_readl(rng_base + reg);
}

static inline void omap_rng_write_reg(int reg, u32 val)
{
        __raw_writel(val, rng_base + reg);
}

static int omap_rng_data_present(struct hwrng *rng, int wait)
{
        int data, i;

        for (i = 0; i < 20; i++) {
                data = omap_rng_read_reg(RNG_STAT_REG) ? 0 : 1;
                if (data || !wait)
                        break;
                /* RNG produces data fast enough (2+ MBit/sec, even
                 * during "rngtest" loads, that these delays don't
                 * seem to trigger.  We *could* use the RNG IRQ, but
                 * that'd be higher overhead ... so why bother?
                 */
                udelay(10);
        }
        return data;
}

static int omap_rng_data_read(struct hwrng *rng, u32 *data)
{
        *data = omap_rng_read_reg(RNG_OUT_REG);

        return 4;
}

static struct hwrng omap_rng_ops = {
        .name           = "omap",
        .data_present   = omap_rng_data_present,
        .data_read      = omap_rng_data_read,
};

static int __devinit omap_rng_probe(struct platform_device *pdev)
{
        struct resource *res;
        int ret;

        /*
         * A bit ugly, and it will never actually happen but there can
         * be only one RNG and this catches any bork
         */
        if (rng_dev)
                return -EBUSY;

        if (cpu_is_omap24xx()) {
                rng_ick = clk_get(&pdev->dev, "ick");
                if (IS_ERR(rng_ick)) {
                        dev_err(&pdev->dev, "Could not get rng_ick\n");
                        ret = PTR_ERR(rng_ick);
                        return ret;
                } else
                        clk_enable(rng_ick);
        }

        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);

        if (!res)
                return -ENOENT;

        if (!request_mem_region(res->start, resource_size(res), pdev->name)) {
                ret = -EBUSY;
                goto err_region;
        }

        dev_set_drvdata(&pdev->dev, res);
        rng_base = ioremap(res->start, resource_size(res));
        if (!rng_base) {
                ret = -ENOMEM;
                goto err_ioremap;
        }

        ret = hwrng_register(&omap_rng_ops);
        if (ret)
                goto err_register;

        dev_info(&pdev->dev, "OMAP Random Number Generator ver. %02x\n",
                omap_rng_read_reg(RNG_REV_REG));
        omap_rng_write_reg(RNG_MASK_REG, 0x1);

        rng_dev = pdev;

        return 0;

err_register:
        iounmap(rng_base);
        rng_base = NULL;
err_ioremap:
        release_mem_region(res->start, resource_size(res));
err_region:
        if (cpu_is_omap24xx()) {
                clk_disable(rng_ick);
                clk_put(rng_ick);
        }
        return ret;
}

static int __exit omap_rng_remove(struct platform_device *pdev)
{
        struct resource *res = dev_get_drvdata(&pdev->dev);

        hwrng_unregister(&omap_rng_ops);

        omap_rng_write_reg(RNG_MASK_REG, 0x0);

        iounmap(rng_base);

        if (cpu_is_omap24xx()) {
                clk_disable(rng_ick);
                clk_put(rng_ick);
        }

        release_mem_region(res->start, resource_size(res));
        rng_base = NULL;

        return 0;
}

#ifdef CONFIG_PM

static int omap_rng_suspend(struct platform_device *pdev, pm_message_t message)
{
        omap_rng_write_reg(RNG_MASK_REG, 0x0);
        return 0;
}

static int omap_rng_resume(struct platform_device *pdev)
{
        omap_rng_write_reg(RNG_MASK_REG, 0x1);
        return 0;
}

#else

#define omap_rng_suspend        NULL
#define omap_rng_resume         NULL

#endif

/* work with hotplug and coldplug */
MODULE_ALIAS("platform:omap_rng");

static struct platform_driver omap_rng_driver = {
        .driver = {
                .name           = "omap_rng",
                .owner          = THIS_MODULE,
        },
        .probe          = omap_rng_probe,
        .remove         = __exit_p(omap_rng_remove),
        .suspend        = omap_rng_suspend,
        .resume         = omap_rng_resume
};

static int __init omap_rng_init(void)
{
        if (!cpu_is_omap16xx() && !cpu_is_omap24xx())
                return -ENODEV;

        return platform_driver_register(&omap_rng_driver);
}

static void __exit omap_rng_exit(void)
{
        platform_driver_unregister(&omap_rng_driver);
}

module_init(omap_rng_init);
module_exit(omap_rng_exit);

MODULE_AUTHOR("Deepak Saxena (and others)");
MODULE_LICENSE("GPL");