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/*
* 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/module.h>
#include <linux/kernel.h>
#include <linux/platform_device.h>
#include <linux/hw_random.h>
#include <linux/io.h>
#include <linux/timeriomem-rng.h>
#include <linux/jiffies.h>
#include <linux/sched.h>
#include <linux/timer.h>
#include <linux/completion.h>
static struct timeriomem_rng_data *timeriomem_rng_data;
static void timeriomem_rng_trigger(unsigned long);
static DEFINE_TIMER(timeriomem_rng_timer, timeriomem_rng_trigger, 0, 0);
/*
* have data return 1, however return 0 if we have nothing
*/
static int timeriomem_rng_data_present(struct hwrng *rng, int wait)
{
if (rng->priv == 0)
return 1;
if (!wait || timeriomem_rng_data->present)
return timeriomem_rng_data->present;
wait_for_completion(&timeriomem_rng_data->completion);
return 1;
}
static int timeriomem_rng_data_read(struct hwrng *rng, u32 *data)
{
unsigned long cur;
s32 delay;
*data = readl(timeriomem_rng_data->address);
if (rng->priv != 0) {
cur = jiffies;
delay = cur - timeriomem_rng_timer.expires;
delay = rng->priv - (delay % rng->priv);
timeriomem_rng_timer.expires = cur + delay;
timeriomem_rng_data->present = 0;
init_completion(&timeriomem_rng_data->completion);
add_timer(&timeriomem_rng_timer);
}
return 4;
}
static void timeriomem_rng_trigger(unsigned long dummy)
{
timeriomem_rng_data->present = 1;
complete(&timeriomem_rng_data->completion);
}
static struct hwrng timeriomem_rng_ops = {
.name = "timeriomem",
.data_present = timeriomem_rng_data_present,
.data_read = timeriomem_rng_data_read,
.priv = 0,
};
static int timeriomem_rng_probe(struct platform_device *pdev)
{
struct resource *res;
int ret;
res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
if (!res)
return -ENOENT;
timeriomem_rng_data = pdev->dev.platform_data;
timeriomem_rng_data->address = ioremap(res->start, resource_size(res));
if (!timeriomem_rng_data->address)
return -EIO;
if (timeriomem_rng_data->period != 0
&& usecs_to_jiffies(timeriomem_rng_data->period) > 0) {
timeriomem_rng_timer.expires = jiffies;
timeriomem_rng_ops.priv = usecs_to_jiffies(
timeriomem_rng_data->period);
}
timeriomem_rng_data->present = 1;
ret = hwrng_register(&timeriomem_rng_ops);
if (ret)
goto failed;
dev_info(&pdev->dev, "32bits from 0x%p @ %dus\n",
timeriomem_rng_data->address,
timeriomem_rng_data->period);
return 0;
failed:
dev_err(&pdev->dev, "problem registering\n");
iounmap(timeriomem_rng_data->address);
return ret;
}
static int timeriomem_rng_remove(struct platform_device *pdev)
{
del_timer_sync(&timeriomem_rng_timer);
hwrng_unregister(&timeriomem_rng_ops);
iounmap(timeriomem_rng_data->address);
return 0;
}
static struct platform_driver timeriomem_rng_driver = {
.driver = {
.name = "timeriomem_rng",
.owner = THIS_MODULE,
},
.probe = timeriomem_rng_probe,
.remove = timeriomem_rng_remove,
};
module_platform_driver(timeriomem_rng_driver);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Alexander Clouter <alex@digriz.org.uk>");
MODULE_DESCRIPTION("Timer IOMEM H/W RNG driver");
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