linux-imx

/*

 * drivers/char/hw_random/timeriomem-rng.c

 *

 * Copyright (C) 2009 Alexander Clouter <alex@digriz.org.uk>

 *

 * Derived from drivers/char/hw_random/omap-rng.c

 *   Copyright 2005 (c) MontaVista Software, Inc.

 *   Author: Deepak Saxena <dsaxena@plexity.net>

 *

 * 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.

 *

 * Overview:

 *   This driver is useful for platforms that have an IO range that provides

 *   periodic random data from a single IO memory address.  All the platform

 *   has to do is provide the address and 'wait time' that new data becomes

 *   available.

 *

 * TODO: add support for reading sizes other than 32bits and masking

 */

​

#include <linux/completion.h>

#include <linux/delay.h>

#include <linux/hrtimer.h>

#include <linux/hw_random.h>

#include <linux/io.h>

#include <linux/ktime.h>

#include <linux/module.h>

#include <linux/of.h>

#include <linux/platform_device.h>

#include <linux/slab.h>

#include <linux/time.h>

#include <linux/timeriomem-rng.h>

​

struct timeriomem_rng_private {

    void __iomem        *io_base;

    ktime_t         period;

    unsigned int        present:1;

​

    struct hrtimer      timer;

    struct completion   completion;

​

    struct hwrng        rng_ops;

};

​

static int timeriomem_rng_read(struct hwrng *hwrng, void *data,

                size_t max, bool wait)

{

    struct timeriomem_rng_private *priv =

        container_of(hwrng, struct timeriomem_rng_private, rng_ops);

    int retval = 0;

    int period_us = ktime_to_us(priv->period);

​

    /*

     * There may not have been enough time for new data to be generated

     * since the last request.  If the caller doesn't want to wait, let them

     * bail out.  Otherwise, wait for the completion.  If the new data has

     * already been generated, the completion should already be available.

     */

    if (!wait && !priv->present)

        return 0;

​