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pasemi-rng.c

/*
 * Copyright (C) 2006-2007 PA Semi, Inc
 *
 * Maintained by: Olof Johansson <olof@lixom.net>
 *
 * Driver for the PWRficient onchip rng
 *
 * 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.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/platform_device.h>
#include <linux/hw_random.h>
#include <asm/of_platform.h>
#include <asm/io.h>

#define SDCRNG_CTL_REG              0x00
#define   SDCRNG_CTL_FVLD_M         0x0000f000
#define   SDCRNG_CTL_FVLD_S         12
#define   SDCRNG_CTL_KSZ            0x00000800
#define   SDCRNG_CTL_RSRC_CRG       0x00000010
#define   SDCRNG_CTL_RSRC_RRG       0x00000000
#define   SDCRNG_CTL_CE             0x00000004
#define   SDCRNG_CTL_RE             0x00000002
#define   SDCRNG_CTL_DR             0x00000001
#define   SDCRNG_CTL_SELECT_RRG_RNG (SDCRNG_CTL_RE | SDCRNG_CTL_RSRC_RRG)
#define   SDCRNG_CTL_SELECT_CRG_RNG (SDCRNG_CTL_CE | SDCRNG_CTL_RSRC_CRG)
#define SDCRNG_VAL_REG              0x20

#define MODULE_NAME "pasemi_rng"

static int pasemi_rng_data_present(struct hwrng *rng)
{
      void __iomem *rng_regs = (void __iomem *)rng->priv;

      return (in_le32(rng_regs + SDCRNG_CTL_REG)
            & SDCRNG_CTL_FVLD_M) ? 1 : 0;
}

static int pasemi_rng_data_read(struct hwrng *rng, u32 *data)
{
      void __iomem *rng_regs = (void __iomem *)rng->priv;
      *data = in_le32(rng_regs + SDCRNG_VAL_REG);
      return 4;
}

static int pasemi_rng_init(struct hwrng *rng)
{
      void __iomem *rng_regs = (void __iomem *)rng->priv;
      u32 ctl;

      ctl = SDCRNG_CTL_DR | SDCRNG_CTL_SELECT_RRG_RNG | SDCRNG_CTL_KSZ;
      out_le32(rng_regs + SDCRNG_CTL_REG, ctl);
      out_le32(rng_regs + SDCRNG_CTL_REG, ctl & ~SDCRNG_CTL_DR);

      return 0;
}

static void pasemi_rng_cleanup(struct hwrng *rng)
{
      void __iomem *rng_regs = (void __iomem *)rng->priv;
      u32 ctl;

      ctl = SDCRNG_CTL_RE | SDCRNG_CTL_CE;
      out_le32(rng_regs + SDCRNG_CTL_REG,
             in_le32(rng_regs + SDCRNG_CTL_REG) & ~ctl);
}

static struct hwrng pasemi_rng = {
      .name       = MODULE_NAME,
      .init       = pasemi_rng_init,
      .cleanup    = pasemi_rng_cleanup,
      .data_present     = pasemi_rng_data_present,
      .data_read  = pasemi_rng_data_read,
};

static int __devinit rng_probe(struct of_device *ofdev,
                         const struct of_device_id *match)
{
      void __iomem *rng_regs;
      struct device_node *rng_np = ofdev->node;
      struct resource res;
      int err = 0;

      err = of_address_to_resource(rng_np, 0, &res);
      if (err)
            return -ENODEV;

      rng_regs = ioremap(res.start, 0x100);

      if (!rng_regs)
            return -ENOMEM;

      pasemi_rng.priv = (unsigned long)rng_regs;

      printk(KERN_INFO "Registering PA Semi RNG\n");

      err = hwrng_register(&pasemi_rng);

      if (err)
            iounmap(rng_regs);

      return err;
}

static int __devexit rng_remove(struct of_device *dev)
{
      void __iomem *rng_regs = (void __iomem *)pasemi_rng.priv;

      hwrng_unregister(&pasemi_rng);
      iounmap(rng_regs);

      return 0;
}

static struct of_device_id rng_match[] = {
      {
            .compatible      = "1682m-rng",
      },
      {},
};

static struct of_platform_driver rng_driver = {
      .name       = "pasemi-rng",
      .match_table      = rng_match,
      .probe            = rng_probe,
      .remove           = rng_remove,
};

static int __init rng_init(void)
{
      return of_register_platform_driver(&rng_driver);
}
module_init(rng_init);

static void __exit rng_exit(void)
{
      of_unregister_platform_driver(&rng_driver);
}
module_exit(rng_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Egor Martovetsky <egor@pasemi.com>");
MODULE_DESCRIPTION("H/W RNG driver for PA Semi processor");

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