169 lines
4.0 KiB
C
169 lines
4.0 KiB
C
/*
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* drivers/char/hw_random/timeriomem-rng.c
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*
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* Copyright (C) 2009 Alexander Clouter <alex@digriz.org.uk>
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*
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* Derived from drivers/char/hw_random/omap-rng.c
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* Copyright 2005 (c) MontaVista Software, Inc.
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* Author: Deepak Saxena <dsaxena@plexity.net>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* Overview:
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* This driver is useful for platforms that have an IO range that provides
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* periodic random data from a single IO memory address. All the platform
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* has to do is provide the address and 'wait time' that new data becomes
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* available.
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*
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* TODO: add support for reading sizes other than 32bits and masking
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*/
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#include <linux/module.h>
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#include <linux/kernel.h>
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#include <linux/platform_device.h>
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#include <linux/hw_random.h>
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#include <linux/io.h>
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#include <linux/timeriomem-rng.h>
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#include <linux/jiffies.h>
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#include <linux/sched.h>
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#include <linux/timer.h>
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#include <linux/completion.h>
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static struct timeriomem_rng_data *timeriomem_rng_data;
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static void timeriomem_rng_trigger(unsigned long);
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static DEFINE_TIMER(timeriomem_rng_timer, timeriomem_rng_trigger, 0, 0);
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/*
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* have data return 1, however return 0 if we have nothing
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*/
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static int timeriomem_rng_data_present(struct hwrng *rng, int wait)
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{
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if (rng->priv == 0)
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return 1;
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if (!wait || timeriomem_rng_data->present)
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return timeriomem_rng_data->present;
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wait_for_completion(&timeriomem_rng_data->completion);
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return 1;
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}
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static int timeriomem_rng_data_read(struct hwrng *rng, u32 *data)
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{
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unsigned long cur;
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s32 delay;
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*data = readl(timeriomem_rng_data->address);
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if (rng->priv != 0) {
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cur = jiffies;
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delay = cur - timeriomem_rng_timer.expires;
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delay = rng->priv - (delay % rng->priv);
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timeriomem_rng_timer.expires = cur + delay;
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timeriomem_rng_data->present = 0;
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init_completion(&timeriomem_rng_data->completion);
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add_timer(&timeriomem_rng_timer);
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}
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return 4;
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}
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static void timeriomem_rng_trigger(unsigned long dummy)
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{
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timeriomem_rng_data->present = 1;
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complete(&timeriomem_rng_data->completion);
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}
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static struct hwrng timeriomem_rng_ops = {
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.name = "timeriomem",
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.data_present = timeriomem_rng_data_present,
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.data_read = timeriomem_rng_data_read,
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.priv = 0,
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};
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static int __devinit timeriomem_rng_probe(struct platform_device *pdev)
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{
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struct resource *res;
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int ret;
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res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
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if (!res)
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return -ENOENT;
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timeriomem_rng_data = pdev->dev.platform_data;
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timeriomem_rng_data->address = ioremap(res->start,
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res->end - res->start + 1);
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if (!timeriomem_rng_data->address)
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return -EIO;
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if (timeriomem_rng_data->period != 0
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&& usecs_to_jiffies(timeriomem_rng_data->period) > 0) {
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timeriomem_rng_timer.expires = jiffies;
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timeriomem_rng_ops.priv = usecs_to_jiffies(
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timeriomem_rng_data->period);
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}
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timeriomem_rng_data->present = 1;
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ret = hwrng_register(&timeriomem_rng_ops);
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if (ret)
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goto failed;
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dev_info(&pdev->dev, "32bits from 0x%p @ %dus\n",
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timeriomem_rng_data->address,
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timeriomem_rng_data->period);
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return 0;
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failed:
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dev_err(&pdev->dev, "problem registering\n");
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iounmap(timeriomem_rng_data->address);
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return ret;
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}
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static int __devexit timeriomem_rng_remove(struct platform_device *pdev)
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{
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del_timer_sync(&timeriomem_rng_timer);
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hwrng_unregister(&timeriomem_rng_ops);
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iounmap(timeriomem_rng_data->address);
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return 0;
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}
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static struct platform_driver timeriomem_rng_driver = {
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.driver = {
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.name = "timeriomem_rng",
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.owner = THIS_MODULE,
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},
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.probe = timeriomem_rng_probe,
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.remove = __devexit_p(timeriomem_rng_remove),
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};
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static int __init timeriomem_rng_init(void)
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{
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return platform_driver_register(&timeriomem_rng_driver);
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}
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static void __exit timeriomem_rng_exit(void)
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{
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platform_driver_unregister(&timeriomem_rng_driver);
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}
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module_init(timeriomem_rng_init);
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module_exit(timeriomem_rng_exit);
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Alexander Clouter <alex@digriz.org.uk>");
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MODULE_DESCRIPTION("Timer IOMEM H/W RNG driver");
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