Initial commit

drivers/char/hw_random/timeriomem-rng.c

@@ -0,0 +1,238 @@
+/*
+ * 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/of.h>
+#include <linux/hw_random.h>
+#include <linux/io.h>
+#include <linux/slab.h>
+#include <linux/timeriomem-rng.h>
+#include <linux/jiffies.h>
+#include <linux/sched.h>
+#include <linux/timer.h>
+#include <linux/completion.h>
+
+struct timeriomem_rng_private_data {
+	void __iomem		*io_base;
+	unsigned int		expires;
+	unsigned int		period;
+	unsigned int		present:1;
+
+	struct timer_list	timer;
+	struct completion	completion;
+
+	struct hwrng		timeriomem_rng_ops;
+};
+
+#define to_rng_priv(rng) \
+		((struct timeriomem_rng_private_data *)rng->priv)
+
+/*
+ * have data return 1, however return 0 if we have nothing
+ */
+static int timeriomem_rng_data_present(struct hwrng *rng, int wait)
+{
+	struct timeriomem_rng_private_data *priv = to_rng_priv(rng);
+
+	if (!wait || priv->present)
+		return priv->present;
+
+	wait_for_completion(&priv->completion);
+
+	return 1;
+}
+
+static int timeriomem_rng_data_read(struct hwrng *rng, u32 *data)
+{
+	struct timeriomem_rng_private_data *priv = to_rng_priv(rng);
+	unsigned long cur;
+	s32 delay;
+
+	*data = readl(priv->io_base);
+
+	cur = jiffies;
+
+	delay = cur - priv->expires;
+	delay = priv->period - (delay % priv->period);
+
+	priv->expires = cur + delay;
+	priv->present = 0;
+
+	INIT_COMPLETION(priv->completion);
+	mod_timer(&priv->timer, priv->expires);
+
+	return 4;
+}
+
+static void timeriomem_rng_trigger(unsigned long data)
+{
+	struct timeriomem_rng_private_data *priv
+			= (struct timeriomem_rng_private_data *)data;
+
+	priv->present = 1;
+	complete(&priv->completion);
+}
+
+static int timeriomem_rng_probe(struct platform_device *pdev)
+{
+	struct timeriomem_rng_data *pdata = pdev->dev.platform_data;
+	struct timeriomem_rng_private_data *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 = kzalloc(sizeof(struct timeriomem_rng_private_data), GFP_KERNEL);
+	if (!priv) {
+		dev_err(&pdev->dev, "failed to allocate device structure.\n");
+		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");
+			err = -EINVAL;
+			goto out_free;
+		}
+	} else
+		period = pdata->period;
+
+	priv->period = usecs_to_jiffies(period);
+	if (priv->period < 1) {
+		dev_err(&pdev->dev, "period is less than one jiffy\n");
+		err = -EINVAL;
+		goto out_free;
+	}
+
+	priv->expires	= jiffies;
+	priv->present	= 1;
+
+	init_completion(&priv->completion);
+	complete(&priv->completion);
+
+	setup_timer(&priv->timer, timeriomem_rng_trigger, (unsigned long)priv);
+
+	priv->timeriomem_rng_ops.name		= dev_name(&pdev->dev);
+	priv->timeriomem_rng_ops.data_present	= timeriomem_rng_data_present;
+	priv->timeriomem_rng_ops.data_read	= timeriomem_rng_data_read;
+	priv->timeriomem_rng_ops.priv		= (unsigned long)priv;
+
+	if (!request_mem_region(res->start, resource_size(res),
+				dev_name(&pdev->dev))) {
+		dev_err(&pdev->dev, "request_mem_region failed\n");
+		err = -EBUSY;
+		goto out_timer;
+	}
+
+	priv->io_base = ioremap(res->start, resource_size(res));
+	if (priv->io_base == NULL) {
+		dev_err(&pdev->dev, "ioremap failed\n");
+		err = -EIO;
+		goto out_release_io;
+	}
+
+	err = hwrng_register(&priv->timeriomem_rng_ops);
+	if (err) {
+		dev_err(&pdev->dev, "problem registering\n");
+		goto out;
+	}
+
+	dev_info(&pdev->dev, "32bits from 0x%p @ %dus\n",
+			priv->io_base, period);
+
+	return 0;
+
+out:
+	iounmap(priv->io_base);
+out_release_io:
+	release_mem_region(res->start, resource_size(res));
+out_timer:
+	del_timer_sync(&priv->timer);
+out_free:
+	platform_set_drvdata(pdev, NULL);
+	kfree(priv);
+	return err;
+}
+
+static int timeriomem_rng_remove(struct platform_device *pdev)
+{
+	struct timeriomem_rng_private_data *priv = platform_get_drvdata(pdev);
+	struct resource *res;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+
+	hwrng_unregister(&priv->timeriomem_rng_ops);
+
+	del_timer_sync(&priv->timer);
+	iounmap(priv->io_base);
+	release_mem_region(res->start, resource_size(res));
+	platform_set_drvdata(pdev, NULL);
+	kfree(priv);
+
+	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",
+		.owner		= THIS_MODULE,
+		.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");