hwrng: timeriomem - New driver

Some hardware platforms, the TS-7800[1] is one for example, can
supply the kernel with an entropy source, albeit a slow one for
TS-7800 users, by just reading a particular IO address.  This
source must not be read above a certain rate otherwise the quality
suffers.

The driver is then hooked into by calling
platform_device_(register|add|del) passing a structure similar to:
------
static struct timeriomem_rng_data ts78xx_ts_rng_data = {
        .address        = (u32 *__iomem) TS_RNG,
        .period         = 1000000, /* one second */
};

static struct platform_device ts78xx_ts_rng_device = {
        .name           = "timeriomem_rng",
        .id             = -1,
        .dev            = {
                .platform_data  = &ts78xx_ts_rng_data,
        },
        .num_resources  = 0,
};
------

[1] http://www.embeddedarm.com/products/board-detail.php?product=TS-7800

Signed-off-by: Alexander Clouter <alex@digriz.org.uk>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
Alexander Clouter 2009-02-22 12:03:56 +08:00 committed by Herbert Xu
parent 0a2e821d62
commit 9c3c133b1e
4 changed files with 187 additions and 0 deletions

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@ -20,6 +20,20 @@ config HW_RANDOM
If unsure, say Y.
config HW_RANDOM_TIMERIOMEM
tristate "Timer IOMEM HW Random Number Generator support"
depends on HW_RANDOM
---help---
This driver provides kernel-side support for a generic Random
Number Generator used by reading a 'dumb' iomem address that
is to be read no faster than, for example, once a second;
the default FPGA bitstream on the TS-7800 has such functionality.
To compile this driver as a module, choose M here: the
module will be called timeriomem-rng.
If unsure, say Y.
config HW_RANDOM_INTEL
tristate "Intel HW Random Number Generator support"
depends on HW_RANDOM && (X86 || IA64) && PCI

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@ -4,6 +4,7 @@
obj-$(CONFIG_HW_RANDOM) += rng-core.o
rng-core-y := core.o
obj-$(CONFIG_HW_RANDOM_TIMERIOMEM) += timeriomem-rng.o
obj-$(CONFIG_HW_RANDOM_INTEL) += intel-rng.o
obj-$(CONFIG_HW_RANDOM_AMD) += amd-rng.o
obj-$(CONFIG_HW_RANDOM_GEODE) += geode-rng.o

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@ -0,0 +1,151 @@
/*
* 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 __init timeriomem_rng_probe(struct platform_device *pdev)
{
int ret;
timeriomem_rng_data = pdev->dev.platform_data;
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) {
dev_err(&pdev->dev, "problem registering\n");
return ret;
}
dev_info(&pdev->dev, "32bits from 0x%p @ %dus\n",
timeriomem_rng_data->address,
timeriomem_rng_data->period);
return 0;
}
static int __devexit timeriomem_rng_remove(struct platform_device *pdev)
{
del_timer_sync(&timeriomem_rng_timer);
hwrng_unregister(&timeriomem_rng_ops);
return 0;
}
static struct platform_driver timeriomem_rng_driver = {
.driver = {
.name = "timeriomem_rng",
.owner = THIS_MODULE,
},
.probe = timeriomem_rng_probe,
.remove = __devexit_p(timeriomem_rng_remove),
};
static int __init timeriomem_rng_init(void)
{
return platform_driver_register(&timeriomem_rng_driver);
}
static void __exit timeriomem_rng_exit(void)
{
platform_driver_unregister(&timeriomem_rng_driver);
}
module_init(timeriomem_rng_init);
module_exit(timeriomem_rng_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Alexander Clouter <alex@digriz.org.uk>");
MODULE_DESCRIPTION("Timer IOMEM H/W RNG driver");

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@ -0,0 +1,21 @@
/*
* linux/include/linux/timeriomem-rng.h
*
* Copyright (c) 2009 Alexander Clouter <alex@digriz.org.uk>
*
* 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.
*/
#include <linux/completion.h>
struct timeriomem_rng_data {
struct completion completion;
unsigned int present:1;
u32 __iomem *address;
/* measures in usecs */
unsigned int period;
};