--- /dev/null
+/*
+ * 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;
+
+ reinit_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 = devm_kzalloc(&pdev->dev,
+ sizeof(struct timeriomem_rng_private_data), 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;
+ }
+ } 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");
+ return -EINVAL;
+ }
+
+ 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;
+
+ priv->io_base = devm_ioremap_resource(&pdev->dev, res);
+ if (IS_ERR(priv->io_base)) {
+ err = PTR_ERR(priv->io_base);
+ goto out_timer;
+ }
+
+ err = hwrng_register(&priv->timeriomem_rng_ops);
+ if (err) {
+ dev_err(&pdev->dev, "problem registering\n");
+ goto out_timer;
+ }
+
+ dev_info(&pdev->dev, "32bits from 0x%p @ %dus\n",
+ priv->io_base, period);
+
+ return 0;
+
+out_timer:
+ del_timer_sync(&priv->timer);
+ return err;
+}
+
+static int timeriomem_rng_remove(struct platform_device *pdev)
+{
+ struct timeriomem_rng_private_data *priv = platform_get_drvdata(pdev);
+
+ hwrng_unregister(&priv->timeriomem_rng_ops);
+
+ del_timer_sync(&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");
Code Review / kvmfornfv.git / blobdiff