Commit | Line | Data |
---|---|---|
c6a97c42 DT |
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/kernel.h> | |
20 | #include <linux/module.h> | |
21 | #include <linux/of_address.h> | |
22 | #include <linux/of_platform.h> | |
23 | #include <linux/pm_runtime.h> | |
24 | #include <linux/slab.h> | |
25 | ||
26 | #define RNG_CR 0x00 | |
27 | #define RNG_CR_RNGEN BIT(2) | |
28 | ||
29 | #define RNG_SR 0x04 | |
30 | #define RNG_SR_SEIS BIT(6) | |
31 | #define RNG_SR_CEIS BIT(5) | |
32 | #define RNG_SR_DRDY BIT(0) | |
33 | ||
34 | #define RNG_DR 0x08 | |
35 | ||
36 | /* | |
37 | * It takes 40 cycles @ 48MHz to generate each random number (e.g. <1us). | |
38 | * At the time of writing STM32 parts max out at ~200MHz meaning a timeout | |
39 | * of 500 leaves us a very comfortable margin for error. The loop to which | |
40 | * the timeout applies takes at least 4 instructions per iteration so the | |
41 | * timeout is enough to take us up to multi-GHz parts! | |
42 | */ | |
43 | #define RNG_TIMEOUT 500 | |
44 | ||
45 | struct stm32_rng_private { | |
46 | struct hwrng rng; | |
47 | void __iomem *base; | |
48 | struct clk *clk; | |
49 | }; | |
50 | ||
51 | static int stm32_rng_read(struct hwrng *rng, void *data, size_t max, bool wait) | |
52 | { | |
53 | struct stm32_rng_private *priv = | |
54 | container_of(rng, struct stm32_rng_private, rng); | |
55 | u32 sr; | |
56 | int retval = 0; | |
57 | ||
58 | pm_runtime_get_sync((struct device *) priv->rng.priv); | |
59 | ||
60 | while (max > sizeof(u32)) { | |
61 | sr = readl_relaxed(priv->base + RNG_SR); | |
62 | if (!sr && wait) { | |
63 | unsigned int timeout = RNG_TIMEOUT; | |
64 | ||
65 | do { | |
66 | cpu_relax(); | |
67 | sr = readl_relaxed(priv->base + RNG_SR); | |
68 | } while (!sr && --timeout); | |
69 | } | |
70 | ||
71 | /* If error detected or data not ready... */ | |
72 | if (sr != RNG_SR_DRDY) | |
73 | break; | |
74 | ||
75 | *(u32 *)data = readl_relaxed(priv->base + RNG_DR); | |
76 | ||
77 | retval += sizeof(u32); | |
78 | data += sizeof(u32); | |
79 | max -= sizeof(u32); | |
80 | } | |
81 | ||
82 | if (WARN_ONCE(sr & (RNG_SR_SEIS | RNG_SR_CEIS), | |
83 | "bad RNG status - %x\n", sr)) | |
84 | writel_relaxed(0, priv->base + RNG_SR); | |
85 | ||
86 | pm_runtime_mark_last_busy((struct device *) priv->rng.priv); | |
87 | pm_runtime_put_sync_autosuspend((struct device *) priv->rng.priv); | |
88 | ||
89 | return retval || !wait ? retval : -EIO; | |
90 | } | |
91 | ||
92 | static int stm32_rng_init(struct hwrng *rng) | |
93 | { | |
94 | struct stm32_rng_private *priv = | |
95 | container_of(rng, struct stm32_rng_private, rng); | |
96 | int err; | |
97 | ||
98 | err = clk_prepare_enable(priv->clk); | |
99 | if (err) | |
100 | return err; | |
101 | ||
102 | writel_relaxed(RNG_CR_RNGEN, priv->base + RNG_CR); | |
103 | ||
104 | /* clear error indicators */ | |
105 | writel_relaxed(0, priv->base + RNG_SR); | |
106 | ||
107 | return 0; | |
108 | } | |
109 | ||
110 | static void stm32_rng_cleanup(struct hwrng *rng) | |
111 | { | |
112 | struct stm32_rng_private *priv = | |
113 | container_of(rng, struct stm32_rng_private, rng); | |
114 | ||
115 | writel_relaxed(0, priv->base + RNG_CR); | |
116 | clk_disable_unprepare(priv->clk); | |
117 | } | |
118 | ||
119 | static int stm32_rng_probe(struct platform_device *ofdev) | |
120 | { | |
121 | struct device *dev = &ofdev->dev; | |
122 | struct device_node *np = ofdev->dev.of_node; | |
123 | struct stm32_rng_private *priv; | |
124 | struct resource res; | |
125 | int err; | |
126 | ||
127 | priv = devm_kzalloc(dev, sizeof(struct stm32_rng_private), GFP_KERNEL); | |
128 | if (!priv) | |
129 | return -ENOMEM; | |
130 | ||
131 | err = of_address_to_resource(np, 0, &res); | |
132 | if (err) | |
133 | return err; | |
134 | ||
135 | priv->base = devm_ioremap_resource(dev, &res); | |
136 | if (IS_ERR(priv->base)) | |
137 | return PTR_ERR(priv->base); | |
138 | ||
139 | priv->clk = devm_clk_get(&ofdev->dev, NULL); | |
140 | if (IS_ERR(priv->clk)) | |
141 | return PTR_ERR(priv->clk); | |
142 | ||
143 | dev_set_drvdata(dev, priv); | |
144 | ||
145 | priv->rng.name = dev_driver_string(dev), | |
146 | #ifndef CONFIG_PM | |
147 | priv->rng.init = stm32_rng_init, | |
148 | priv->rng.cleanup = stm32_rng_cleanup, | |
149 | #endif | |
150 | priv->rng.read = stm32_rng_read, | |
151 | priv->rng.priv = (unsigned long) dev; | |
152 | ||
153 | pm_runtime_set_autosuspend_delay(dev, 100); | |
154 | pm_runtime_use_autosuspend(dev); | |
155 | pm_runtime_enable(dev); | |
156 | ||
157 | return devm_hwrng_register(dev, &priv->rng); | |
158 | } | |
159 | ||
160 | #ifdef CONFIG_PM | |
161 | static int stm32_rng_runtime_suspend(struct device *dev) | |
162 | { | |
d6ba06b8 | 163 | struct stm32_rng_private *priv = dev_get_drvdata(dev); |
c6a97c42 DT |
164 | |
165 | stm32_rng_cleanup(&priv->rng); | |
166 | ||
167 | return 0; | |
168 | } | |
169 | ||
170 | static int stm32_rng_runtime_resume(struct device *dev) | |
171 | { | |
d6ba06b8 | 172 | struct stm32_rng_private *priv = dev_get_drvdata(dev); |
c6a97c42 DT |
173 | |
174 | return stm32_rng_init(&priv->rng); | |
175 | } | |
176 | #endif | |
177 | ||
178 | static UNIVERSAL_DEV_PM_OPS(stm32_rng_pm_ops, stm32_rng_runtime_suspend, | |
179 | stm32_rng_runtime_resume, NULL); | |
180 | ||
181 | static const struct of_device_id stm32_rng_match[] = { | |
182 | { | |
183 | .compatible = "st,stm32-rng", | |
184 | }, | |
185 | {}, | |
186 | }; | |
187 | MODULE_DEVICE_TABLE(of, stm32_rng_match); | |
188 | ||
189 | static struct platform_driver stm32_rng_driver = { | |
190 | .driver = { | |
191 | .name = "stm32-rng", | |
192 | .pm = &stm32_rng_pm_ops, | |
193 | .of_match_table = stm32_rng_match, | |
194 | }, | |
195 | .probe = stm32_rng_probe, | |
196 | }; | |
197 | ||
198 | module_platform_driver(stm32_rng_driver); | |
199 | ||
200 | MODULE_LICENSE("GPL"); | |
201 | MODULE_AUTHOR("Daniel Thompson <daniel.thompson@linaro.org>"); | |
202 | MODULE_DESCRIPTION("STMicroelectronics STM32 RNG device driver"); |