1 // SPDX-License-Identifier: GPL-2.0-or-later OR MIT
2 /*
3 * Copyright (c) 2023 David Yang
4 */
5
6 #include <linux/err.h>
7 #include <linux/hw_random.h>
8 #include <linux/io.h>
9 #include <linux/iopoll.h>
10 #include <linux/kernel.h>
11 #include <linux/module.h>
12 #include <linux/platform_device.h>
13
14 #define RNG_CTRL 0x0
15 #define RNG_SOURCE GENMASK(1, 0)
16 #define DROP_ENABLE BIT(5)
17 #define POST_PROCESS_ENABLE BIT(7)
18 #define POST_PROCESS_DEPTH GENMASK(15, 8)
19 #define RNG_NUMBER 0x4
20 #define RNG_STAT 0x8
21 #define DATA_COUNT GENMASK(2, 0) /* max 4 */
22
23 struct histb_rng_priv {
24 struct hwrng rng;
25 void __iomem *base;
26 };
27
28 /*
29 * Observed:
30 * depth = 1 -> ~1ms
31 * depth = 255 -> ~16ms
32 */
histb_rng_wait(void __iomem * base)33 static int histb_rng_wait(void __iomem *base)
34 {
35 u32 val;
36
37 return readl_relaxed_poll_timeout(base + RNG_STAT, val,
38 val & DATA_COUNT, 1000, 30 * 1000);
39 }
40
histb_rng_init(void __iomem * base,unsigned int depth)41 static void histb_rng_init(void __iomem *base, unsigned int depth)
42 {
43 u32 val;
44
45 val = readl_relaxed(base + RNG_CTRL);
46
47 val &= ~RNG_SOURCE;
48 val |= 2;
49
50 val &= ~POST_PROCESS_DEPTH;
51 val |= min(depth, 0xffu) << 8;
52
53 val |= POST_PROCESS_ENABLE;
54 val |= DROP_ENABLE;
55
56 writel_relaxed(val, base + RNG_CTRL);
57 }
58
histb_rng_read(struct hwrng * rng,void * data,size_t max,bool wait)59 static int histb_rng_read(struct hwrng *rng, void *data, size_t max, bool wait)
60 {
61 struct histb_rng_priv *priv = container_of(rng, typeof(*priv), rng);
62 void __iomem *base = priv->base;
63
64 for (int i = 0; i < max; i += sizeof(u32)) {
65 if (!(readl_relaxed(base + RNG_STAT) & DATA_COUNT)) {
66 if (!wait)
67 return i;
68 if (histb_rng_wait(base)) {
69 pr_err("failed to generate random number, generated %d\n",
70 i);
71 return i ? i : -ETIMEDOUT;
72 }
73 }
74 *(u32 *) (data + i) = readl_relaxed(base + RNG_NUMBER);
75 }
76
77 return max;
78 }
79
histb_rng_get_depth(void __iomem * base)80 static unsigned int histb_rng_get_depth(void __iomem *base)
81 {
82 return (readl_relaxed(base + RNG_CTRL) & POST_PROCESS_DEPTH) >> 8;
83 }
84
85 static ssize_t
depth_show(struct device * dev,struct device_attribute * attr,char * buf)86 depth_show(struct device *dev, struct device_attribute *attr, char *buf)
87 {
88 struct histb_rng_priv *priv = dev_get_drvdata(dev);
89 void __iomem *base = priv->base;
90
91 return sprintf(buf, "%u\n", histb_rng_get_depth(base));
92 }
93
94 static ssize_t
depth_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)95 depth_store(struct device *dev, struct device_attribute *attr,
96 const char *buf, size_t count)
97 {
98 struct histb_rng_priv *priv = dev_get_drvdata(dev);
99 void __iomem *base = priv->base;
100 unsigned int depth;
101
102 if (kstrtouint(buf, 0, &depth))
103 return -ERANGE;
104
105 histb_rng_init(base, depth);
106 return count;
107 }
108
109 static DEVICE_ATTR_RW(depth);
110
111 static struct attribute *histb_rng_attrs[] = {
112 &dev_attr_depth.attr,
113 NULL,
114 };
115
116 ATTRIBUTE_GROUPS(histb_rng);
117
histb_rng_probe(struct platform_device * pdev)118 static int histb_rng_probe(struct platform_device *pdev)
119 {
120 struct device *dev = &pdev->dev;
121 struct histb_rng_priv *priv;
122 void __iomem *base;
123 int ret;
124
125 priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
126 if (!priv)
127 return -ENOMEM;
128
129 base = devm_platform_ioremap_resource(pdev, 0);
130 if (IS_ERR(base))
131 return PTR_ERR(base);
132
133 histb_rng_init(base, 144);
134 if (histb_rng_wait(base)) {
135 dev_err(dev, "cannot bring up device\n");
136 return -ENODEV;
137 }
138
139 priv->base = base;
140 priv->rng.name = pdev->name;
141 priv->rng.read = histb_rng_read;
142 ret = devm_hwrng_register(dev, &priv->rng);
143 if (ret) {
144 dev_err(dev, "failed to register hwrng: %d\n", ret);
145 return ret;
146 }
147
148 platform_set_drvdata(pdev, priv);
149 dev_set_drvdata(dev, priv);
150 return 0;
151 }
152
153 static const struct of_device_id histb_rng_of_match[] = {
154 { .compatible = "hisilicon,histb-rng", },
155 { }
156 };
157 MODULE_DEVICE_TABLE(of, histb_rng_of_match);
158
159 static struct platform_driver histb_rng_driver = {
160 .probe = histb_rng_probe,
161 .driver = {
162 .name = "histb-rng",
163 .of_match_table = histb_rng_of_match,
164 .dev_groups = histb_rng_groups,
165 },
166 };
167
168 module_platform_driver(histb_rng_driver);
169
170 MODULE_DESCRIPTION("Hisilicon STB random number generator driver");
171 MODULE_LICENSE("Dual MIT/GPL");
172 MODULE_AUTHOR("David Yang <mmyangfl@gmail.com>");
173