1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * drivers/char/hw_random/timeriomem-rng.c
  4 *
  5 * Copyright (C) 2009 Alexander Clouter <alex@digriz.org.uk>
  6 *
  7 * Derived from drivers/char/hw_random/omap-rng.c
  8 *   Copyright 2005 (c) MontaVista Software, Inc.
  9 *   Author: Deepak Saxena <dsaxena@plexity.net>
 10 *
 
 
 
 
 11 * Overview:
 12 *   This driver is useful for platforms that have an IO range that provides
 13 *   periodic random data from a single IO memory address.  All the platform
 14 *   has to do is provide the address and 'wait time' that new data becomes
 15 *   available.
 16 *
 17 * TODO: add support for reading sizes other than 32bits and masking
 18 */
 19
 20#include <linux/completion.h>
 21#include <linux/delay.h>
 22#include <linux/hrtimer.h>
 23#include <linux/hw_random.h>
 24#include <linux/io.h>
 25#include <linux/ktime.h>
 26#include <linux/module.h>
 27#include <linux/of.h>
 28#include <linux/platform_device.h>
 
 
 
 29#include <linux/slab.h>
 30#include <linux/time.h>
 31#include <linux/timeriomem-rng.h>
 
 
 
 
 32
 33struct timeriomem_rng_private {
 34	void __iomem		*io_base;
 35	ktime_t			period;
 
 36	unsigned int		present:1;
 37
 38	struct hrtimer		timer;
 39	struct completion	completion;
 40
 41	struct hwrng		rng_ops;
 42};
 43
 44static int timeriomem_rng_read(struct hwrng *hwrng, void *data,
 45				size_t max, bool wait)
 
 
 
 
 
 46{
 47	struct timeriomem_rng_private *priv =
 48		container_of(hwrng, struct timeriomem_rng_private, rng_ops);
 49	int retval = 0;
 50	int period_us = ktime_to_us(priv->period);
 51
 52	/*
 53	 * There may not have been enough time for new data to be generated
 54	 * since the last request.  If the caller doesn't want to wait, let them
 55	 * bail out.  Otherwise, wait for the completion.  If the new data has
 56	 * already been generated, the completion should already be available.
 57	 */
 58	if (!wait && !priv->present)
 59		return 0;
 60
 61	wait_for_completion(&priv->completion);
 62
 63	do {
 64		/*
 65		 * After the first read, all additional reads will need to wait
 66		 * for the RNG to generate new data.  Since the period can have
 67		 * a wide range of values (1us to 1s have been observed), allow
 68		 * for 1% tolerance in the sleep time rather than a fixed value.
 69		 */
 70		if (retval > 0)
 71			usleep_range(period_us,
 72					period_us + max(1, period_us / 100));
 73
 74		*(u32 *)data = readl(priv->io_base);
 75		retval += sizeof(u32);
 76		data += sizeof(u32);
 77		max -= sizeof(u32);
 78	} while (wait && max > sizeof(u32));
 79
 80	/*
 81	 * Block any new callers until the RNG has had time to generate new
 82	 * data.
 83	 */
 84	priv->present = 0;
 
 85	reinit_completion(&priv->completion);
 86	hrtimer_forward_now(&priv->timer, priv->period);
 87	hrtimer_restart(&priv->timer);
 88
 89	return retval;
 90}
 91
 92static enum hrtimer_restart timeriomem_rng_trigger(struct hrtimer *timer)
 93{
 94	struct timeriomem_rng_private *priv
 95		= container_of(timer, struct timeriomem_rng_private, timer);
 96
 97	priv->present = 1;
 98	complete(&priv->completion);
 99
100	return HRTIMER_NORESTART;
101}
102
103static int timeriomem_rng_probe(struct platform_device *pdev)
104{
105	struct timeriomem_rng_data *pdata = pdev->dev.platform_data;
106	struct timeriomem_rng_private *priv;
107	struct resource *res;
108	int err = 0;
109	int period;
110
111	if (!pdev->dev.of_node && !pdata) {
112		dev_err(&pdev->dev, "timeriomem_rng_data is missing\n");
113		return -EINVAL;
114	}
115
 
 
 
 
 
 
 
 
 
 
116	/* Allocate memory for the device structure (and zero it) */
117	priv = devm_kzalloc(&pdev->dev,
118			sizeof(struct timeriomem_rng_private), GFP_KERNEL);
119	if (!priv)
120		return -ENOMEM;
121
122	platform_set_drvdata(pdev, priv);
123
124	priv->io_base = devm_platform_get_and_ioremap_resource(pdev, 0, &res);
125	if (IS_ERR(priv->io_base))
126		return PTR_ERR(priv->io_base);
127
128	if (res->start % 4 != 0 || resource_size(res) < 4) {
129		dev_err(&pdev->dev,
130			"address must be at least four bytes wide and 32-bit aligned\n");
131		return -EINVAL;
132	}
133
134	if (pdev->dev.of_node) {
135		int i;
136
137		if (!of_property_read_u32(pdev->dev.of_node,
138						"period", &i))
139			period = i;
140		else {
141			dev_err(&pdev->dev, "missing period\n");
142			return -EINVAL;
143		}
144
145		if (!of_property_read_u32(pdev->dev.of_node,
146						"quality", &i))
147			priv->rng_ops.quality = i;
148	} else {
149		period = pdata->period;
150		priv->rng_ops.quality = pdata->quality;
151	}
152
153	priv->period = ns_to_ktime(period * NSEC_PER_USEC);
154	init_completion(&priv->completion);
155	hrtimer_init(&priv->timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
156	priv->timer.function = timeriomem_rng_trigger;
 
157
158	priv->rng_ops.name = dev_name(&pdev->dev);
159	priv->rng_ops.read = timeriomem_rng_read;
160
161	/* Assume random data is already available. */
162	priv->present = 1;
163	complete(&priv->completion);
164
165	err = devm_hwrng_register(&pdev->dev, &priv->rng_ops);
 
 
 
 
 
 
 
 
 
 
 
 
 
166	if (err) {
167		dev_err(&pdev->dev, "problem registering\n");
168		return err;
169	}
170
171	dev_info(&pdev->dev, "32bits from 0x%p @ %dus\n",
172			priv->io_base, period);
173
174	return 0;
 
 
 
 
175}
176
177static void timeriomem_rng_remove(struct platform_device *pdev)
178{
179	struct timeriomem_rng_private *priv = platform_get_drvdata(pdev);
 
 
180
181	hrtimer_cancel(&priv->timer);
 
 
182}
183
184static const struct of_device_id timeriomem_rng_match[] = {
185	{ .compatible = "timeriomem_rng" },
186	{},
187};
188MODULE_DEVICE_TABLE(of, timeriomem_rng_match);
189
190static struct platform_driver timeriomem_rng_driver = {
191	.driver = {
192		.name		= "timeriomem_rng",
193		.of_match_table	= timeriomem_rng_match,
194	},
195	.probe		= timeriomem_rng_probe,
196	.remove_new	= timeriomem_rng_remove,
197};
198
199module_platform_driver(timeriomem_rng_driver);
200
201MODULE_LICENSE("GPL");
202MODULE_AUTHOR("Alexander Clouter <alex@digriz.org.uk>");
203MODULE_DESCRIPTION("Timer IOMEM H/W RNG driver");

 
  1/*
  2 * drivers/char/hw_random/timeriomem-rng.c
  3 *
  4 * Copyright (C) 2009 Alexander Clouter <alex@digriz.org.uk>
  5 *
  6 * Derived from drivers/char/hw_random/omap-rng.c
  7 *   Copyright 2005 (c) MontaVista Software, Inc.
  8 *   Author: Deepak Saxena <dsaxena@plexity.net>
  9 *
 10 * This program is free software; you can redistribute it and/or modify
 11 * it under the terms of the GNU General Public License version 2 as
 12 * published by the Free Software Foundation.
 13 *
 14 * Overview:
 15 *   This driver is useful for platforms that have an IO range that provides
 16 *   periodic random data from a single IO memory address.  All the platform
 17 *   has to do is provide the address and 'wait time' that new data becomes
 18 *   available.
 19 *
 20 * TODO: add support for reading sizes other than 32bits and masking
 21 */
 22
 
 
 
 
 
 
 23#include <linux/module.h>
 24#include <linux/kernel.h>
 25#include <linux/platform_device.h>
 26#include <linux/of.h>
 27#include <linux/hw_random.h>
 28#include <linux/io.h>
 29#include <linux/slab.h>
 
 30#include <linux/timeriomem-rng.h>
 31#include <linux/jiffies.h>
 32#include <linux/sched.h>
 33#include <linux/timer.h>
 34#include <linux/completion.h>
 35
 36struct timeriomem_rng_private_data {
 37	void __iomem		*io_base;
 38	unsigned int		expires;
 39	unsigned int		period;
 40	unsigned int		present:1;
 41
 42	struct timer_list	timer;
 43	struct completion	completion;
 44
 45	struct hwrng		timeriomem_rng_ops;
 46};
 47
 48#define to_rng_priv(rng) \
 49		((struct timeriomem_rng_private_data *)rng->priv)
 50
 51/*
 52 * have data return 1, however return 0 if we have nothing
 53 */
 54static int timeriomem_rng_data_present(struct hwrng *rng, int wait)
 55{
 56	struct timeriomem_rng_private_data *priv = to_rng_priv(rng);
 57
 58	if (!wait || priv->present)
 59		return priv->present;
 
 
 
 
 
 
 
 
 
 60
 61	wait_for_completion(&priv->completion);
 62
 63	return 1;
 64}
 65
 66static int timeriomem_rng_data_read(struct hwrng *rng, u32 *data)
 67{
 68	struct timeriomem_rng_private_data *priv = to_rng_priv(rng);
 69	unsigned long cur;
 70	s32 delay;
 71
 72	*data = readl(priv->io_base);
 73
 74	cur = jiffies;
 75
 76	delay = cur - priv->expires;
 77	delay = priv->period - (delay % priv->period);
 78
 79	priv->expires = cur + delay;
 
 
 
 
 80	priv->present = 0;
 81
 82	reinit_completion(&priv->completion);
 83	mod_timer(&priv->timer, priv->expires);
 
 84
 85	return 4;
 86}
 87
 88static void timeriomem_rng_trigger(unsigned long data)
 89{
 90	struct timeriomem_rng_private_data *priv
 91			= (struct timeriomem_rng_private_data *)data;
 92
 93	priv->present = 1;
 94	complete(&priv->completion);
 
 
 95}
 96
 97static int timeriomem_rng_probe(struct platform_device *pdev)
 98{
 99	struct timeriomem_rng_data *pdata = pdev->dev.platform_data;
100	struct timeriomem_rng_private_data *priv;
101	struct resource *res;
102	int err = 0;
103	int period;
104
105	if (!pdev->dev.of_node && !pdata) {
106		dev_err(&pdev->dev, "timeriomem_rng_data is missing\n");
107		return -EINVAL;
108	}
109
110	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
111	if (!res)
112		return -ENXIO;
113
114	if (res->start % 4 != 0 || resource_size(res) != 4) {
115		dev_err(&pdev->dev,
116			"address must be four bytes wide and aligned\n");
117		return -EINVAL;
118	}
119
120	/* Allocate memory for the device structure (and zero it) */
121	priv = devm_kzalloc(&pdev->dev,
122			sizeof(struct timeriomem_rng_private_data), GFP_KERNEL);
123	if (!priv)
124		return -ENOMEM;
125
126	platform_set_drvdata(pdev, priv);
127
 
 
 
 
 
 
 
 
 
 
128	if (pdev->dev.of_node) {
129		int i;
130
131		if (!of_property_read_u32(pdev->dev.of_node,
132						"period", &i))
133			period = i;
134		else {
135			dev_err(&pdev->dev, "missing period\n");
136			return -EINVAL;
137		}
 
 
 
 
138	} else {
139		period = pdata->period;
 
140	}
141
142	priv->period = usecs_to_jiffies(period);
143	if (priv->period < 1) {
144		dev_err(&pdev->dev, "period is less than one jiffy\n");
145		return -EINVAL;
146	}
147
148	priv->expires	= jiffies;
149	priv->present	= 1;
150
151	init_completion(&priv->completion);
 
152	complete(&priv->completion);
153
154	setup_timer(&priv->timer, timeriomem_rng_trigger, (unsigned long)priv);
155
156	priv->timeriomem_rng_ops.name		= dev_name(&pdev->dev);
157	priv->timeriomem_rng_ops.data_present	= timeriomem_rng_data_present;
158	priv->timeriomem_rng_ops.data_read	= timeriomem_rng_data_read;
159	priv->timeriomem_rng_ops.priv		= (unsigned long)priv;
160
161	priv->io_base = devm_ioremap_resource(&pdev->dev, res);
162	if (IS_ERR(priv->io_base)) {
163		err = PTR_ERR(priv->io_base);
164		goto out_timer;
165	}
166
167	err = hwrng_register(&priv->timeriomem_rng_ops);
168	if (err) {
169		dev_err(&pdev->dev, "problem registering\n");
170		goto out_timer;
171	}
172
173	dev_info(&pdev->dev, "32bits from 0x%p @ %dus\n",
174			priv->io_base, period);
175
176	return 0;
177
178out_timer:
179	del_timer_sync(&priv->timer);
180	return err;
181}
182
183static int timeriomem_rng_remove(struct platform_device *pdev)
184{
185	struct timeriomem_rng_private_data *priv = platform_get_drvdata(pdev);
186
187	hwrng_unregister(&priv->timeriomem_rng_ops);
188
189	del_timer_sync(&priv->timer);
190
191	return 0;
192}
193
194static const struct of_device_id timeriomem_rng_match[] = {
195	{ .compatible = "timeriomem_rng" },
196	{},
197};
198MODULE_DEVICE_TABLE(of, timeriomem_rng_match);
199
200static struct platform_driver timeriomem_rng_driver = {
201	.driver = {
202		.name		= "timeriomem_rng",
203		.of_match_table	= timeriomem_rng_match,
204	},
205	.probe		= timeriomem_rng_probe,
206	.remove		= timeriomem_rng_remove,
207};
208
209module_platform_driver(timeriomem_rng_driver);
210
211MODULE_LICENSE("GPL");
212MODULE_AUTHOR("Alexander Clouter <alex@digriz.org.uk>");
213MODULE_DESCRIPTION("Timer IOMEM H/W RNG driver");