atmel-rng.c

  1/*
  2 * Copyright (c) 2011 Peter Korsgaard <jacmet@sunsite.dk>
  3 *
  4 * This file is licensed under  the terms of the GNU General Public
  5 * License version 2. This program is licensed "as is" without any
  6 * warranty of any kind, whether express or implied.
  7 */
  8
  9#include <linux/kernel.h>
 10#include <linux/module.h>
 11#include <linux/mod_devicetable.h>
 12#include <linux/slab.h>
 13#include <linux/err.h>
 14#include <linux/clk.h>
 15#include <linux/io.h>
 16#include <linux/iopoll.h>
 17#include <linux/hw_random.h>
 18#include <linux/of.h>
 19#include <linux/platform_device.h>
 20#include <linux/pm_runtime.h>
 21
 22#define TRNG_CR		0x00
 23#define TRNG_MR		0x04
 24#define TRNG_ISR	0x1c
 25#define TRNG_ISR_DATRDY	BIT(0)
 26#define TRNG_ODATA	0x50
 27
 28#define TRNG_KEY	0x524e4700 /* RNG */
 29
 30#define TRNG_HALFR	BIT(0) /* generate RN every 168 cycles */
 31
 32struct atmel_trng_data {
 33	bool has_half_rate;
 34};
 35
 36struct atmel_trng {
 37	struct clk *clk;
 38	void __iomem *base;
 39	struct hwrng rng;
 40	struct device *dev;
 41	bool has_half_rate;
 42};
 43
 44static bool atmel_trng_wait_ready(struct atmel_trng *trng, bool wait)
 45{
 46	int ready;
 47
 48	ready = readl(trng->base + TRNG_ISR) & TRNG_ISR_DATRDY;
 49	if (!ready && wait)
 50		readl_poll_timeout(trng->base + TRNG_ISR, ready,
 51				   ready & TRNG_ISR_DATRDY, 1000, 20000);
 52
 53	return !!ready;
 54}
 55
 56static int atmel_trng_read(struct hwrng *rng, void *buf, size_t max,
 57			   bool wait)
 58{
 59	struct atmel_trng *trng = container_of(rng, struct atmel_trng, rng);
 60	u32 *data = buf;
 61	int ret;
 62
 63	ret = pm_runtime_get_sync(trng->dev);
 64	if (ret < 0) {
 65		pm_runtime_put_sync(trng->dev);
 66		return ret;
 67	}
 68
 69	ret = atmel_trng_wait_ready(trng, wait);
 70	if (!ret)
 71		goto out;
 72
 73	*data = readl(trng->base + TRNG_ODATA);
 74	/*
 75	 * ensure data ready is only set again AFTER the next data word is ready
 76	 * in case it got set between checking ISR and reading ODATA, so we
 77	 * don't risk re-reading the same word
 78	 */
 79	readl(trng->base + TRNG_ISR);
 80	ret = 4;
 81
 82out:
 83	pm_runtime_put_sync_autosuspend(trng->dev);
 84	return ret;
 85}
 86
 87static int atmel_trng_init(struct atmel_trng *trng)
 88{
 89	unsigned long rate;
 90	int ret;
 91
 92	ret = clk_prepare_enable(trng->clk);
 93	if (ret)
 94		return ret;
 95
 96	if (trng->has_half_rate) {
 97		rate = clk_get_rate(trng->clk);
 98
 99		/* if peripheral clk is above 100MHz, set HALFR */
100		if (rate > 100000000)
101			writel(TRNG_HALFR, trng->base + TRNG_MR);
102	}
103
104	writel(TRNG_KEY | 1, trng->base + TRNG_CR);
105
106	return 0;
107}
108
109static void atmel_trng_cleanup(struct atmel_trng *trng)
110{
111	writel(TRNG_KEY, trng->base + TRNG_CR);
112	clk_disable_unprepare(trng->clk);
113}
114
115static int atmel_trng_probe(struct platform_device *pdev)
116{
117	struct atmel_trng *trng;
118	const struct atmel_trng_data *data;
119	int ret;
120
121	trng = devm_kzalloc(&pdev->dev, sizeof(*trng), GFP_KERNEL);
122	if (!trng)
123		return -ENOMEM;
124
125	trng->base = devm_platform_ioremap_resource(pdev, 0);
126	if (IS_ERR(trng->base))
127		return PTR_ERR(trng->base);
128
129	trng->clk = devm_clk_get(&pdev->dev, NULL);
130	if (IS_ERR(trng->clk))
131		return PTR_ERR(trng->clk);
132	data = of_device_get_match_data(&pdev->dev);
133	if (!data)
134		return -ENODEV;
135
136	trng->has_half_rate = data->has_half_rate;
137	trng->dev = &pdev->dev;
138	trng->rng.name = pdev->name;
139	trng->rng.read = atmel_trng_read;
140	platform_set_drvdata(pdev, trng);
141
142#ifndef CONFIG_PM
143	ret = atmel_trng_init(trng);
144	if (ret)
145		return ret;
146#endif
147
148	pm_runtime_set_autosuspend_delay(&pdev->dev, 100);
149	pm_runtime_use_autosuspend(&pdev->dev);
150	pm_runtime_enable(&pdev->dev);
151
152	ret = devm_hwrng_register(&pdev->dev, &trng->rng);
153	if (ret) {
154		pm_runtime_disable(&pdev->dev);
155		pm_runtime_set_suspended(&pdev->dev);
156#ifndef CONFIG_PM
157		atmel_trng_cleanup(trng);
158#endif
159	}
160
161	return ret;
162}
163
164static void atmel_trng_remove(struct platform_device *pdev)
165{
166	struct atmel_trng *trng = platform_get_drvdata(pdev);
167
168	atmel_trng_cleanup(trng);
169	pm_runtime_disable(&pdev->dev);
170	pm_runtime_set_suspended(&pdev->dev);
171}
172
173static int __maybe_unused atmel_trng_runtime_suspend(struct device *dev)
174{
175	struct atmel_trng *trng = dev_get_drvdata(dev);
176
177	atmel_trng_cleanup(trng);
178
179	return 0;
180}
181
182static int __maybe_unused atmel_trng_runtime_resume(struct device *dev)
183{
184	struct atmel_trng *trng = dev_get_drvdata(dev);
185
186	return atmel_trng_init(trng);
187}
188
189static const struct dev_pm_ops __maybe_unused atmel_trng_pm_ops = {
190	SET_RUNTIME_PM_OPS(atmel_trng_runtime_suspend,
191			   atmel_trng_runtime_resume, NULL)
192	SET_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend,
193				pm_runtime_force_resume)
194};
195
196static const struct atmel_trng_data at91sam9g45_config = {
197	.has_half_rate = false,
198};
199
200static const struct atmel_trng_data sam9x60_config = {
201	.has_half_rate = true,
202};
203
204static const struct of_device_id atmel_trng_dt_ids[] = {
205	{
206		.compatible = "atmel,at91sam9g45-trng",
207		.data = &at91sam9g45_config,
208	}, {
209		.compatible = "microchip,sam9x60-trng",
210		.data = &sam9x60_config,
211	}, {
212		/* sentinel */
213	}
214};
215MODULE_DEVICE_TABLE(of, atmel_trng_dt_ids);
216
217static struct platform_driver atmel_trng_driver = {
218	.probe		= atmel_trng_probe,
219	.remove		= atmel_trng_remove,
220	.driver		= {
221		.name	= "atmel-trng",
222		.pm	= pm_ptr(&atmel_trng_pm_ops),
223		.of_match_table = atmel_trng_dt_ids,
224	},
225};
226
227module_platform_driver(atmel_trng_driver);
228
229MODULE_LICENSE("GPL");
230MODULE_AUTHOR("Peter Korsgaard <jacmet@sunsite.dk>");
231MODULE_DESCRIPTION("Atmel true random number generator driver");