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omap-rng.c

/*
 * drivers/char/hw_random/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.
 *
 * TODO:
 *
 * - Make status updated be interrupt driven so we don't poll
 *
 */

#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 <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 u32 omap_rng_read_reg(int reg)
{
      return __raw_readl(rng_base + reg);
}

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

/* REVISIT: Does the status bit really work on 16xx? */
static int omap_rng_data_present(struct hwrng *rng)
{
      return omap_rng_read_reg(RNG_STAT_REG) ? 0 : 1;
}

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 __init omap_rng_probe(struct platform_device *pdev)
{
      struct resource *res, *mem;
      int ret;

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

      if (cpu_is_omap24xx()) {
            rng_ick = clk_get(NULL, "rng_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;

      mem = request_mem_region(res->start, res->end - res->start + 1,
                         pdev->name);
      if (mem == NULL)
            return -EBUSY;

      dev_set_drvdata(&pdev->dev, mem);
      rng_base = (u32 __iomem *)io_p2v(res->start);

      ret = hwrng_register(&omap_rng_ops);
      if (ret) {
            release_resource(mem);
            rng_base = NULL;
            return ret;
      }

      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;
}

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

      hwrng_unregister(&omap_rng_ops);

      omap_rng_write_reg(RNG_MASK_REG, 0x0);

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

      release_resource(mem);
      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


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");

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