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Commit 9c3c133b authored by Alexander Clouter's avatar Alexander Clouter Committed by Herbert Xu
Browse files

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: default avatarAlexander Clouter <alex@digriz.org.uk>
Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
parent 0a2e821d

drivers/char/hw_random/Kconfig

+14 −0
Original line number Diff line number Diff line
@@ -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

drivers/char/hw_random/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -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

drivers/char/hw_random/timeriomem-rng.c

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+151 −0
Original line number Diff line number Diff line 
/*

 * 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");

include/linux/timeriomem-rng.h

0 → 100644
+21 −0
Original line number Diff line number Diff line 
/*

 * 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;

};