1 files changed, 216 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 000000000..ba01f24db
--- /dev/null
+++ b/drivers/char/hw_random/timeriomem-rng.c
@@ -0,0 +1,216 @@
+/*
+ * 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/completion.h>
+#include <linux/delay.h>
+#include <linux/hrtimer.h>
+#include <linux/hw_random.h>
+#include <linux/io.h>
+#include <linux/ktime.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <linux/time.h>
+#include <linux/timeriomem-rng.h>
+
+struct timeriomem_rng_private {
+	void __iomem		*io_base;
+	ktime_t			period;
+	unsigned int		present:1;
+
+	struct hrtimer		timer;
+	struct completion	completion;
+
+	struct hwrng		rng_ops;
+};
+
+static int timeriomem_rng_read(struct hwrng *hwrng, void *data,
+				size_t max, bool wait)
+{
+	struct timeriomem_rng_private *priv =
+		container_of(hwrng, struct timeriomem_rng_private, rng_ops);
+	int retval = 0;
+	int period_us = ktime_to_us(priv->period);
+
+	/*
+	 * There may not have been enough time for new data to be generated
+	 * since the last request.  If the caller doesn't want to wait, let them
+	 * bail out.  Otherwise, wait for the completion.  If the new data has
+	 * already been generated, the completion should already be available.
+	 */
+	if (!wait && !priv->present)
+		return 0;
+
+	wait_for_completion(&priv->completion);
+
+	do {
+		/*
+		 * After the first read, all additional reads will need to wait
+		 * for the RNG to generate new data.  Since the period can have
+		 * a wide range of values (1us to 1s have been observed), allow
+		 * for 1% tolerance in the sleep time rather than a fixed value.
+		 */
+		if (retval > 0)
+			usleep_range(period_us,
+					period_us + max(1, period_us / 100));
+
+		*(u32 *)data = readl(priv->io_base);
+		retval += sizeof(u32);
+		data += sizeof(u32);
+		max -= sizeof(u32);
+	} while (wait && max > sizeof(u32));
+
+	/*
+	 * Block any new callers until the RNG has had time to generate new
+	 * data.
+	 */
+	priv->present = 0;
+	reinit_completion(&priv->completion);
+	hrtimer_forward_now(&priv->timer, priv->period);
+	hrtimer_restart(&priv->timer);
+
+	return retval;
+}
+
+static enum hrtimer_restart timeriomem_rng_trigger(struct hrtimer *timer)
+{
+	struct timeriomem_rng_private *priv
+		= container_of(timer, struct timeriomem_rng_private, timer);
+
+	priv->present = 1;
+	complete(&priv->completion);
+
+	return HRTIMER_NORESTART;
+}
+
+static int timeriomem_rng_probe(struct platform_device *pdev)
+{
+	struct timeriomem_rng_data *pdata = pdev->dev.platform_data;
+	struct timeriomem_rng_private *priv;
+	struct resource *res;
+	int err = 0;
+	int period;
+
+	if (!pdev->dev.of_node && !pdata) {
+		dev_err(&pdev->dev, "timeriomem_rng_data is missing\n");
+		return -EINVAL;
+	}
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!res)
+		return -ENXIO;
+
+	if (res->start % 4 != 0 || resource_size(res) != 4) {
+		dev_err(&pdev->dev,
+			"address must be four bytes wide and aligned\n");
+		return -EINVAL;
+	}
+
+	/* Allocate memory for the device structure (and zero it) */
+	priv = devm_kzalloc(&pdev->dev,
+			sizeof(struct timeriomem_rng_private), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	platform_set_drvdata(pdev, priv);
+
+	if (pdev->dev.of_node) {
+		int i;
+
+		if (!of_property_read_u32(pdev->dev.of_node,
+						"period", &i))
+			period = i;
+		else {
+			dev_err(&pdev->dev, "missing period\n");
+			return -EINVAL;
+		}
+
+		if (!of_property_read_u32(pdev->dev.of_node,
+						"quality", &i))
+			priv->rng_ops.quality = i;
+		else
+			priv->rng_ops.quality = 0;
+	} else {
+		period = pdata->period;
+		priv->rng_ops.quality = pdata->quality;
+	}
+
+	priv->period = ns_to_ktime(period * NSEC_PER_USEC);
+	init_completion(&priv->completion);
+	hrtimer_init(&priv->timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
+	priv->timer.function = timeriomem_rng_trigger;
+
+	priv->rng_ops.name = dev_name(&pdev->dev);
+	priv->rng_ops.read = timeriomem_rng_read;
+
+	priv->io_base = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(priv->io_base)) {
+		return PTR_ERR(priv->io_base);
+	}
+
+	/* Assume random data is already available. */
+	priv->present = 1;
+	complete(&priv->completion);
+
+	err = hwrng_register(&priv->rng_ops);
+	if (err) {
+		dev_err(&pdev->dev, "problem registering\n");
+		return err;
+	}
+
+	dev_info(&pdev->dev, "32bits from 0x%p @ %dus\n",
+			priv->io_base, period);
+
+	return 0;
+}
+
+static int timeriomem_rng_remove(struct platform_device *pdev)
+{
+	struct timeriomem_rng_private *priv = platform_get_drvdata(pdev);
+
+	hwrng_unregister(&priv->rng_ops);
+	hrtimer_cancel(&priv->timer);
+
+	return 0;
+}
+
+static const struct of_device_id timeriomem_rng_match[] = {
+	{ .compatible = "timeriomem_rng" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, timeriomem_rng_match);
+
+static struct platform_driver timeriomem_rng_driver = {
+	.driver = {
+		.name		= "timeriomem_rng",
+		.of_match_table	= timeriomem_rng_match,
+	},
+	.probe		= timeriomem_rng_probe,
+	.remove		= timeriomem_rng_remove,
+};
+
+module_platform_driver(timeriomem_rng_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Alexander Clouter <alex@digriz.org.uk>");
+MODULE_DESCRIPTION("Timer IOMEM H/W RNG driver");