1 /*
2  * Copyright (c) 2015, Daniel Thompson
3  *
4  * This file is free software; you can redistribute it and/or
5  * modify it under the terms of the GNU General Public License
6  * as published by the Free Software Foundation; either version 2
7  * of the License, or (at your option) any later version.
8  *
9  * This file is distributed in the hope that it will be useful,
10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
12  * GNU General Public License for more details.
13  */
14 
15 #include <linux/clk.h>
16 #include <linux/delay.h>
17 #include <linux/hw_random.h>
18 #include <linux/io.h>
19 #include <linux/iopoll.h>
20 #include <linux/kernel.h>
21 #include <linux/module.h>
22 #include <linux/of_address.h>
23 #include <linux/of_platform.h>
24 #include <linux/pm_runtime.h>
25 #include <linux/reset.h>
26 #include <linux/slab.h>
27 
28 #define RNG_CR 0x00
29 #define RNG_CR_RNGEN BIT(2)
30 #define RNG_CR_CED BIT(5)
31 
32 #define RNG_SR 0x04
33 #define RNG_SR_SEIS BIT(6)
34 #define RNG_SR_CEIS BIT(5)
35 #define RNG_SR_DRDY BIT(0)
36 
37 #define RNG_DR 0x08
38 
39 struct stm32_rng_private {
40 	struct hwrng rng;
41 	void __iomem *base;
42 	struct clk *clk;
43 	struct reset_control *rst;
44 	bool ced;
45 };
46 
47 static int stm32_rng_read(struct hwrng *rng, void *data, size_t max, bool wait)
48 {
49 	struct stm32_rng_private *priv =
50 	    container_of(rng, struct stm32_rng_private, rng);
51 	u32 sr;
52 	int retval = 0;
53 
54 	pm_runtime_get_sync((struct device *) priv->rng.priv);
55 
56 	while (max > sizeof(u32)) {
57 		sr = readl_relaxed(priv->base + RNG_SR);
58 		/* Manage timeout which is based on timer and take */
59 		/* care of initial delay time when enabling rng	*/
60 		if (!sr && wait) {
61 			retval = readl_relaxed_poll_timeout_atomic(priv->base
62 								   + RNG_SR,
63 								   sr, sr,
64 								   10, 50000);
65 			if (retval)
66 				dev_err((struct device *)priv->rng.priv,
67 					"%s: timeout %x!\n", __func__, sr);
68 		}
69 
70 		/* If error detected or data not ready... */
71 		if (sr != RNG_SR_DRDY) {
72 			if (WARN_ONCE(sr & (RNG_SR_SEIS | RNG_SR_CEIS),
73 					"bad RNG status - %x\n", sr))
74 				writel_relaxed(0, priv->base + RNG_SR);
75 			break;
76 		}
77 
78 		*(u32 *)data = readl_relaxed(priv->base + RNG_DR);
79 
80 		retval += sizeof(u32);
81 		data += sizeof(u32);
82 		max -= sizeof(u32);
83 	}
84 
85 	pm_runtime_mark_last_busy((struct device *) priv->rng.priv);
86 	pm_runtime_put_sync_autosuspend((struct device *) priv->rng.priv);
87 
88 	return retval || !wait ? retval : -EIO;
89 }
90 
91 static int stm32_rng_init(struct hwrng *rng)
92 {
93 	struct stm32_rng_private *priv =
94 	    container_of(rng, struct stm32_rng_private, rng);
95 	int err;
96 
97 	err = clk_prepare_enable(priv->clk);
98 	if (err)
99 		return err;
100 
101 	if (priv->ced)
102 		writel_relaxed(RNG_CR_RNGEN, priv->base + RNG_CR);
103 	else
104 		writel_relaxed(RNG_CR_RNGEN | RNG_CR_CED,
105 			       priv->base + RNG_CR);
106 
107 	/* clear error indicators */
108 	writel_relaxed(0, priv->base + RNG_SR);
109 
110 	return 0;
111 }
112 
113 static void stm32_rng_cleanup(struct hwrng *rng)
114 {
115 	struct stm32_rng_private *priv =
116 	    container_of(rng, struct stm32_rng_private, rng);
117 
118 	writel_relaxed(0, priv->base + RNG_CR);
119 	clk_disable_unprepare(priv->clk);
120 }
121 
122 static int stm32_rng_probe(struct platform_device *ofdev)
123 {
124 	struct device *dev = &ofdev->dev;
125 	struct device_node *np = ofdev->dev.of_node;
126 	struct stm32_rng_private *priv;
127 	struct resource res;
128 	int err;
129 
130 	priv = devm_kzalloc(dev, sizeof(struct stm32_rng_private), GFP_KERNEL);
131 	if (!priv)
132 		return -ENOMEM;
133 
134 	err = of_address_to_resource(np, 0, &res);
135 	if (err)
136 		return err;
137 
138 	priv->base = devm_ioremap_resource(dev, &res);
139 	if (IS_ERR(priv->base))
140 		return PTR_ERR(priv->base);
141 
142 	priv->clk = devm_clk_get(&ofdev->dev, NULL);
143 	if (IS_ERR(priv->clk))
144 		return PTR_ERR(priv->clk);
145 
146 	priv->rst = devm_reset_control_get(&ofdev->dev, NULL);
147 	if (!IS_ERR(priv->rst)) {
148 		reset_control_assert(priv->rst);
149 		udelay(2);
150 		reset_control_deassert(priv->rst);
151 	}
152 
153 	priv->ced = of_property_read_bool(np, "clock-error-detect");
154 
155 	dev_set_drvdata(dev, priv);
156 
157 	priv->rng.name = dev_driver_string(dev),
158 #ifndef CONFIG_PM
159 	priv->rng.init = stm32_rng_init,
160 	priv->rng.cleanup = stm32_rng_cleanup,
161 #endif
162 	priv->rng.read = stm32_rng_read,
163 	priv->rng.priv = (unsigned long) dev;
164 
165 	pm_runtime_set_autosuspend_delay(dev, 100);
166 	pm_runtime_use_autosuspend(dev);
167 	pm_runtime_enable(dev);
168 
169 	return devm_hwrng_register(dev, &priv->rng);
170 }
171 
172 #ifdef CONFIG_PM
173 static int stm32_rng_runtime_suspend(struct device *dev)
174 {
175 	struct stm32_rng_private *priv = dev_get_drvdata(dev);
176 
177 	stm32_rng_cleanup(&priv->rng);
178 
179 	return 0;
180 }
181 
182 static int stm32_rng_runtime_resume(struct device *dev)
183 {
184 	struct stm32_rng_private *priv = dev_get_drvdata(dev);
185 
186 	return stm32_rng_init(&priv->rng);
187 }
188 #endif
189 
190 static const struct dev_pm_ops stm32_rng_pm_ops = {
191 	SET_RUNTIME_PM_OPS(stm32_rng_runtime_suspend,
192 			   stm32_rng_runtime_resume, NULL)
193 	SET_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend,
194 				pm_runtime_force_resume)
195 };
196 
197 
198 static const struct of_device_id stm32_rng_match[] = {
199 	{
200 		.compatible = "st,stm32-rng",
201 	},
202 	{},
203 };
204 MODULE_DEVICE_TABLE(of, stm32_rng_match);
205 
206 static struct platform_driver stm32_rng_driver = {
207 	.driver = {
208 		.name = "stm32-rng",
209 		.pm = &stm32_rng_pm_ops,
210 		.of_match_table = stm32_rng_match,
211 	},
212 	.probe = stm32_rng_probe,
213 };
214 
215 module_platform_driver(stm32_rng_driver);
216 
217 MODULE_LICENSE("GPL");
218 MODULE_AUTHOR("Daniel Thompson <daniel.thompson@linaro.org>");
219 MODULE_DESCRIPTION("STMicroelectronics STM32 RNG device driver");
220