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 
31 struct 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 
stm32_rng_read(struct hwrng * rng,void * data,size_t max,bool wait)39 static 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 
stm32_rng_init(struct hwrng * rng)85 static 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 
stm32_rng_cleanup(struct hwrng * rng)107 static 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 
stm32_rng_probe(struct platform_device * ofdev)116 static 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 
stm32_rng_remove(struct platform_device * ofdev)167 static 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
stm32_rng_runtime_suspend(struct device * dev)175 static 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 
stm32_rng_runtime_resume(struct device * dev)184 static 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 
192 static 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 
200 static const struct of_device_id stm32_rng_match[] = {
201 	{
202 		.compatible = "st,stm32-rng",
203 	},
204 	{},
205 };
206 MODULE_DEVICE_TABLE(of, stm32_rng_match);
207 
208 static 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 
218 module_platform_driver(stm32_rng_driver);
219 
220 MODULE_LICENSE("GPL");
221 MODULE_AUTHOR("Daniel Thompson <daniel.thompson@linaro.org>");
222 MODULE_DESCRIPTION("STMicroelectronics STM32 RNG device driver");
223