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authorAlexander Clouter <alex@digriz.org.uk>2009-02-22 12:03:56 +0800
committerHerbert Xu <herbert@gondor.apana.org.au>2009-02-22 12:03:56 +0800
commit9c3c133b1ed6e6d01bfabb6de29bf3d0f0886354 (patch)
tree2e6b7184477f75820ce0947df0786920880e4d42 /drivers/char/hw_random/timeriomem-rng.c
parent0a2e821d627ad5ced23cf31137625b81cc205e0f (diff)
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>
Diffstat (limited to 'drivers/char/hw_random/timeriomem-rng.c')
-rw-r--r--drivers/char/hw_random/timeriomem-rng.c151
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 00000000000..10ad41be589
--- /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");