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Date: Sat, 7 Feb 2009 09:53:17 +0000
From: Alexander Clouter <alex@...riz.org.uk>
To: linux-kernel@...r.kernel.org
Cc: akpm@...ux-foundation.org
Subject: [PATCHv2] hw_random: add timeriomem-rng 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@...riz.org.uk>
---
drivers/char/hw_random/Kconfig | 14 +++
drivers/char/hw_random/Makefile | 1 +
drivers/char/hw_random/timeriomem-rng.c | 151 +++++++++++++++++++++++++++++++
include/linux/timeriomem-rng.h | 16 ++++
4 files changed, 182 insertions(+), 0 deletions(-)
create mode 100644 drivers/char/hw_random/timeriomem-rng.c
create mode 100644 include/linux/timeriomem-rng.h
diff --git a/drivers/char/hw_random/Kconfig b/drivers/char/hw_random/Kconfig
index 8822eca..e86dd42 100644
--- a/drivers/char/hw_random/Kconfig
+++ b/drivers/char/hw_random/Kconfig
@@ -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
diff --git a/drivers/char/hw_random/Makefile b/drivers/char/hw_random/Makefile
index b6effb7..e81d21a 100644
--- a/drivers/char/hw_random/Makefile
+++ b/drivers/char/hw_random/Makefile
@@ -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
diff --git a/drivers/char/hw_random/timeriomem-rng.c b/drivers/char/hw_random/timeriomem-rng.c
new file mode 100644
index 0000000..06131fa
--- /dev/null
+++ b/drivers/char/hw_random/timeriomem-rng.c
@@ -0,0 +1,151 @@
+/*
+ * drivers/char/hw_random/timeriomem-rng.c
+ *
+ * Copyright (C) 2008 Alexander Clouter <alex@...riz.org.uk>
+ *
+ * Derived from drivers/char/hw_random/omap-rng.c
+ * Copyright 2005 (c) MontaVista Software, Inc.
+ * Author: Deepak Saxena <dsaxena@...xity.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>
+
+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)
+{
+ s32 delay;
+
+ if (rng->priv == 0)
+ return 1;
+
+ if (del_timer_sync(&timeriomem_rng_timer)) {
+ if (!wait)
+ return 0;
+
+ delay = timeriomem_rng_timer.expires - jiffies;
+
+ schedule_timeout_uninterruptible(delay);
+ }
+
+ 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;
+ add_timer(&timeriomem_rng_timer);
+ }
+
+ return 4;
+}
+
+static void timeriomem_rng_trigger(unsigned long dummy)
+{
+ del_timer_sync(&timeriomem_rng_timer);
+}
+
+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);
+ }
+
+ 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@...riz.org.uk>");
+MODULE_DESCRIPTION("Timer IOMEM H/W RNG driver");
diff --git a/include/linux/timeriomem-rng.h b/include/linux/timeriomem-rng.h
new file mode 100644
index 0000000..16dd9e4
--- /dev/null
+++ b/include/linux/timeriomem-rng.h
@@ -0,0 +1,16 @@
+/*
+ * linux/include/linux/timeriomem-rng.h
+ *
+ * Copyright (c) 2008 Alexander Clouter <alex@...riz.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.
+ */
+
+struct timeriomem_rng_data {
+ u32 __iomem *address;
+
+ /* measures in usecs */
+ unsigned int period;
+};
--
1.5.6.5
--
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