diff options
Diffstat (limited to 'drivers/char/hw_random/timeriomem-rng.c')
| -rw-r--r-- | drivers/char/hw_random/timeriomem-rng.c | 151 |
1 files changed, 151 insertions, 0 deletions
diff --git a/drivers/char/hw_random/timeriomem-rng.c b/drivers/char/hw_random/timeriomem-rng.c new file mode 100644 index 000000000000..10ad41be5897 --- /dev/null +++ b/drivers/char/hw_random/timeriomem-rng.c @@ -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"); |