1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * Copyright (c) 2015, Daniel Thompson
4 */
5
6#include <linux/clk.h>
7#include <linux/delay.h>
8#include <linux/hw_random.h>
9#include <linux/io.h>
10#include <linux/iopoll.h>
11#include <linux/kernel.h>
12#include <linux/module.h>
13#include <linux/of.h>
14#include <linux/of_address.h>
15#include <linux/platform_device.h>
16#include <linux/pm_runtime.h>
17#include <linux/reset.h>
18#include <linux/slab.h>
19
20#define RNG_CR 0x00
21#define RNG_CR_RNGEN BIT(2)
22#define RNG_CR_CED BIT(5)
23
24#define RNG_SR 0x04
25#define RNG_SR_SEIS BIT(6)
26#define RNG_SR_CEIS BIT(5)
27#define RNG_SR_DRDY BIT(0)
28
29#define RNG_DR 0x08
30
31struct stm32_rng_private {
32	struct hwrng rng;
33	void __iomem *base;
34	struct clk *clk;
35	struct reset_control *rst;
36	bool ced;
37};
38
39static int stm32_rng_read(struct hwrng *rng, void *data, size_t max, bool wait)
40{
41	struct stm32_rng_private *priv =
42	    container_of(rng, struct stm32_rng_private, rng);
43	u32 sr;
44	int retval = 0;
45
46	pm_runtime_get_sync((struct device *) priv->rng.priv);
47
48	while (max >= sizeof(u32)) {
49		sr = readl_relaxed(priv->base + RNG_SR);
50		/* Manage timeout which is based on timer and take */
51		/* care of initial delay time when enabling rng	*/
52		if (!sr && wait) {
53			int err;
54
55			err = readl_relaxed_poll_timeout_atomic(priv->base
56								   + RNG_SR,
57								   sr, sr,
58								   10, 50000);
59			if (err)
60				dev_err((struct device *)priv->rng.priv,
61					"%s: timeout %x!\n", __func__, sr);
62		}
63
64		/* If error detected or data not ready... */
65		if (sr != RNG_SR_DRDY) {
66			if (WARN_ONCE(sr & (RNG_SR_SEIS | RNG_SR_CEIS),
67					"bad RNG status - %x\n", sr))
68				writel_relaxed(0, priv->base + RNG_SR);
69			break;
70		}
71
72		*(u32 *)data = readl_relaxed(priv->base + RNG_DR);
73
74		retval += sizeof(u32);
75		data += sizeof(u32);
76		max -= sizeof(u32);
77	}
78
79	pm_runtime_mark_last_busy((struct device *) priv->rng.priv);
80	pm_runtime_put_sync_autosuspend((struct device *) priv->rng.priv);
81
82	return retval || !wait ? retval : -EIO;
83}
84
85static int stm32_rng_init(struct hwrng *rng)
86{
87	struct stm32_rng_private *priv =
88	    container_of(rng, struct stm32_rng_private, rng);
89	int err;
90
91	err = clk_prepare_enable(priv->clk);
92	if (err)
93		return err;
94
95	if (priv->ced)
96		writel_relaxed(RNG_CR_RNGEN, priv->base + RNG_CR);
97	else
98		writel_relaxed(RNG_CR_RNGEN | RNG_CR_CED,
99			       priv->base + RNG_CR);
100
101	/* clear error indicators */
102	writel_relaxed(0, priv->base + RNG_SR);
103
104	return 0;
105}
106
107static void stm32_rng_cleanup(struct hwrng *rng)
108{
109	struct stm32_rng_private *priv =
110	    container_of(rng, struct stm32_rng_private, rng);
111
112	writel_relaxed(0, priv->base + RNG_CR);
113	clk_disable_unprepare(priv->clk);
114}
115
116static int stm32_rng_probe(struct platform_device *ofdev)
117{
118	struct device *dev = &ofdev->dev;
119	struct device_node *np = ofdev->dev.of_node;
120	struct stm32_rng_private *priv;
121	struct resource res;
122	int err;
123
124	priv = devm_kzalloc(dev, sizeof(struct stm32_rng_private), GFP_KERNEL);
125	if (!priv)
126		return -ENOMEM;
127
128	err = of_address_to_resource(np, 0, &res);
129	if (err)
130		return err;
131
132	priv->base = devm_ioremap_resource(dev, &res);
133	if (IS_ERR(priv->base))
134		return PTR_ERR(priv->base);
135
136	priv->clk = devm_clk_get(&ofdev->dev, NULL);
137	if (IS_ERR(priv->clk))
138		return PTR_ERR(priv->clk);
139
140	priv->rst = devm_reset_control_get(&ofdev->dev, NULL);
141	if (!IS_ERR(priv->rst)) {
142		reset_control_assert(priv->rst);
143		udelay(2);
144		reset_control_deassert(priv->rst);
145	}
146
147	priv->ced = of_property_read_bool(np, "clock-error-detect");
148
149	dev_set_drvdata(dev, priv);
150
151	priv->rng.name = dev_driver_string(dev);
152#ifndef CONFIG_PM
153	priv->rng.init = stm32_rng_init;
154	priv->rng.cleanup = stm32_rng_cleanup;
155#endif
156	priv->rng.read = stm32_rng_read;
157	priv->rng.priv = (unsigned long) dev;
158	priv->rng.quality = 900;
159
160	pm_runtime_set_autosuspend_delay(dev, 100);
161	pm_runtime_use_autosuspend(dev);
162	pm_runtime_enable(dev);
163
164	return devm_hwrng_register(dev, &priv->rng);
165}
166
167static int stm32_rng_remove(struct platform_device *ofdev)
168{
169	pm_runtime_disable(&ofdev->dev);
170
171	return 0;
172}
173
174#ifdef CONFIG_PM
175static int stm32_rng_runtime_suspend(struct device *dev)
176{
177	struct stm32_rng_private *priv = dev_get_drvdata(dev);
178
179	stm32_rng_cleanup(&priv->rng);
180
181	return 0;
182}
183
184static int stm32_rng_runtime_resume(struct device *dev)
185{
186	struct stm32_rng_private *priv = dev_get_drvdata(dev);
187
188	return stm32_rng_init(&priv->rng);
189}
190#endif
191
192static const struct dev_pm_ops stm32_rng_pm_ops = {
193	SET_RUNTIME_PM_OPS(stm32_rng_runtime_suspend,
194			   stm32_rng_runtime_resume, NULL)
195	SET_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend,
196				pm_runtime_force_resume)
197};
198
199
200static const struct of_device_id stm32_rng_match[] = {
201	{
202		.compatible = "st,stm32-rng",
203	},
204	{},
205};
206MODULE_DEVICE_TABLE(of, stm32_rng_match);
207
208static struct platform_driver stm32_rng_driver = {
209	.driver = {
210		.name = "stm32-rng",
211		.pm = &stm32_rng_pm_ops,
212		.of_match_table = stm32_rng_match,
213	},
214	.probe = stm32_rng_probe,
215	.remove = stm32_rng_remove,
216};
217
218module_platform_driver(stm32_rng_driver);
219
220MODULE_LICENSE("GPL");
221MODULE_AUTHOR("Daniel Thompson <daniel.thompson@linaro.org>");
222MODULE_DESCRIPTION("STMicroelectronics STM32 RNG device driver");
223