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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/of.h>
#include <linux/hw_random.h>
#include <linux/io.h>
#include <linux/slab.h>
#include <linux/timeriomem-rng.h>
#include <linux/jiffies.h>
#include <linux/sched.h>
#include <linux/timer.h>
#include <linux/completion.h>
struct timeriomem_rng_private_data {
void __iomem *io_base;
unsigned int expires;
unsigned int period;
unsigned int present:1;
struct timer_list timer;
struct completion completion;
struct hwrng timeriomem_rng_ops;
};
#define to_rng_priv(rng) \
((struct timeriomem_rng_private_data *)rng->priv)
/*
* have data return 1, however return 0 if we have nothing
*/
static int timeriomem_rng_data_present(struct hwrng *rng, int wait)
{
struct timeriomem_rng_private_data *priv = to_rng_priv(rng);
if (!wait || priv->present)
return priv->present;
wait_for_completion(&priv->completion);
return 1;
}
static int timeriomem_rng_data_read(struct hwrng *rng, u32 *data)
{
struct timeriomem_rng_private_data *priv = to_rng_priv(rng);
unsigned long cur;
s32 delay;
*data = readl(priv->io_base);
cur = jiffies;
delay = cur - priv->expires;
delay = priv->period - (delay % priv->period);
priv->expires = cur + delay;
priv->present = 0;
reinit_completion(&priv->completion);
mod_timer(&priv->timer, priv->expires);
return 4;
}
static void timeriomem_rng_trigger(unsigned long data)
{
struct timeriomem_rng_private_data *priv
= (struct timeriomem_rng_private_data *)data;
priv->present = 1;
complete(&priv->completion);
}
static int timeriomem_rng_probe(struct platform_device *pdev)
{
struct timeriomem_rng_data *pdata = pdev->dev.platform_data;
struct timeriomem_rng_private_data *priv;
struct resource *res;
int err = 0;
int period;
if (!pdev->dev.of_node && !pdata) {
dev_err(&pdev->dev, "timeriomem_rng_data is missing\n");
return -EINVAL;
}
res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
if (!res)
return -ENXIO;
if (res->start % 4 != 0 || resource_size(res) != 4) {
dev_err(&pdev->dev,
"address must be four bytes wide and aligned\n");
return -EINVAL;
}
/* Allocate memory for the device structure (and zero it) */
priv = devm_kzalloc(&pdev->dev,
sizeof(struct timeriomem_rng_private_data), GFP_KERNEL);
if (!priv)
return -ENOMEM;
platform_set_drvdata(pdev, priv);
if (pdev->dev.of_node) {
int i;
if (!of_property_read_u32(pdev->dev.of_node,
"period", &i))
period = i;
else {
dev_err(&pdev->dev, "missing period\n");
return -EINVAL;
}
} else {
period = pdata->period;
}
priv->period = usecs_to_jiffies(period);
if (priv->period < 1) {
dev_err(&pdev->dev, "period is less than one jiffy\n");
return -EINVAL;
}
priv->expires = jiffies;
priv->present = 1;
init_completion(&priv->completion);
complete(&priv->completion);
setup_timer(&priv->timer, timeriomem_rng_trigger, (unsigned long)priv);
priv->timeriomem_rng_ops.name = dev_name(&pdev->dev);
priv->timeriomem_rng_ops.data_present = timeriomem_rng_data_present;
priv->timeriomem_rng_ops.data_read = timeriomem_rng_data_read;
priv->timeriomem_rng_ops.priv = (unsigned long)priv;
priv->io_base = devm_ioremap_resource(&pdev->dev, res);
if (IS_ERR(priv->io_base)) {
err = PTR_ERR(priv->io_base);
goto out_timer;
}
err = hwrng_register(&priv->timeriomem_rng_ops);
if (err) {
dev_err(&pdev->dev, "problem registering\n");
goto out_timer;
}
dev_info(&pdev->dev, "32bits from 0x%p @ %dus\n",
priv->io_base, period);
return 0;
out_timer:
del_timer_sync(&priv->timer);
return err;
}
static int timeriomem_rng_remove(struct platform_device *pdev)
{
struct timeriomem_rng_private_data *priv = platform_get_drvdata(pdev);
hwrng_unregister(&priv->timeriomem_rng_ops);
del_timer_sync(&priv->timer);
return 0;
}
static const struct of_device_id timeriomem_rng_match[] = {
{ .compatible = "timeriomem_rng" },
{},
};
MODULE_DEVICE_TABLE(of, timeriomem_rng_match);
static struct platform_driver timeriomem_rng_driver = {
.driver = {
.name = "timeriomem_rng",
.of_match_table = timeriomem_rng_match,
},
.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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