blob: 1d35363d23c51929eff4d1924bed08684a6587cc [file] [log] [blame]
Lee Jones4a4da532015-09-17 14:45:55 +01001/*
2 * ST Random Number Generator Driver ST's Platforms
3 *
4 * Author: Pankaj Dev: <pankaj.dev@st.com>
5 * Lee Jones <lee.jones@linaro.org>
6 *
7 * Copyright (C) 2015 STMicroelectronics (R&D) Limited
8 *
9 * This program is free software; you can redistribute it and/or modify
10 * it under the terms of the GNU General Public License version 2 as
11 * published by the Free Software Foundation.
12 */
13
14#include <linux/clk.h>
15#include <linux/delay.h>
16#include <linux/hw_random.h>
17#include <linux/io.h>
18#include <linux/module.h>
19#include <linux/of.h>
20#include <linux/platform_device.h>
21#include <linux/slab.h>
22
23/* Registers */
24#define ST_RNG_STATUS_REG 0x20
25#define ST_RNG_DATA_REG 0x24
26
27/* Registers fields */
28#define ST_RNG_STATUS_BAD_SEQUENCE BIT(0)
29#define ST_RNG_STATUS_BAD_ALTERNANCE BIT(1)
30#define ST_RNG_STATUS_FIFO_FULL BIT(5)
31
Lee Jones4a4da532015-09-17 14:45:55 +010032#define ST_RNG_SAMPLE_SIZE 2 /* 2 Byte (16bit) samples */
Lee Jones9ad92bd2015-10-07 13:23:29 +010033#define ST_RNG_FIFO_DEPTH 4
34#define ST_RNG_FIFO_SIZE (ST_RNG_FIFO_DEPTH * ST_RNG_SAMPLE_SIZE)
Lee Jones4a4da532015-09-17 14:45:55 +010035
Lee Jones93d649b2015-10-07 13:23:28 +010036/*
37 * Samples are documented to be available every 0.667us, so in theory
38 * the 4 sample deep FIFO should take 2.668us to fill. However, during
39 * thorough testing, it became apparent that filling the FIFO actually
40 * takes closer to 12us. We then multiply by 2 in order to account for
41 * the lack of udelay()'s reliability, suggested by Russell King.
42 */
43#define ST_RNG_FILL_FIFO_TIMEOUT (12 * 2)
Lee Jones4a4da532015-09-17 14:45:55 +010044
45struct st_rng_data {
46 void __iomem *base;
47 struct clk *clk;
48 struct hwrng ops;
49};
50
51static int st_rng_read(struct hwrng *rng, void *data, size_t max, bool wait)
52{
53 struct st_rng_data *ddata = (struct st_rng_data *)rng->priv;
54 u32 status;
55 int i;
56
57 if (max < sizeof(u16))
58 return -EINVAL;
59
60 /* Wait until FIFO is full - max 4uS*/
61 for (i = 0; i < ST_RNG_FILL_FIFO_TIMEOUT; i++) {
62 status = readl_relaxed(ddata->base + ST_RNG_STATUS_REG);
63 if (status & ST_RNG_STATUS_FIFO_FULL)
64 break;
65 udelay(1);
66 }
67
68 if (i == ST_RNG_FILL_FIFO_TIMEOUT)
69 return 0;
70
71 for (i = 0; i < ST_RNG_FIFO_SIZE && i < max; i += 2)
72 *(u16 *)(data + i) =
73 readl_relaxed(ddata->base + ST_RNG_DATA_REG);
74
75 return i; /* No of bytes read */
76}
77
78static int st_rng_probe(struct platform_device *pdev)
79{
80 struct st_rng_data *ddata;
81 struct resource *res;
82 struct clk *clk;
83 void __iomem *base;
84 int ret;
85
86 ddata = devm_kzalloc(&pdev->dev, sizeof(*ddata), GFP_KERNEL);
87 if (!ddata)
88 return -ENOMEM;
89
90 res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
91 base = devm_ioremap_resource(&pdev->dev, res);
92 if (IS_ERR(base))
93 return PTR_ERR(base);
94
95 clk = devm_clk_get(&pdev->dev, NULL);
96 if (IS_ERR(clk))
97 return PTR_ERR(clk);
98
99 ret = clk_prepare_enable(clk);
100 if (ret)
101 return ret;
102
103 ddata->ops.priv = (unsigned long)ddata;
104 ddata->ops.read = st_rng_read;
105 ddata->ops.name = pdev->name;
106 ddata->base = base;
107 ddata->clk = clk;
108
109 dev_set_drvdata(&pdev->dev, ddata);
110
111 ret = hwrng_register(&ddata->ops);
112 if (ret) {
113 dev_err(&pdev->dev, "Failed to register HW RNG\n");
114 return ret;
115 }
116
117 dev_info(&pdev->dev, "Successfully registered HW RNG\n");
118
119 return 0;
120}
121
122static int st_rng_remove(struct platform_device *pdev)
123{
124 struct st_rng_data *ddata = dev_get_drvdata(&pdev->dev);
125
126 hwrng_unregister(&ddata->ops);
127
128 clk_disable_unprepare(ddata->clk);
129
130 return 0;
131}
132
133static const struct of_device_id st_rng_match[] = {
134 { .compatible = "st,rng" },
135 {},
136};
137MODULE_DEVICE_TABLE(of, st_rng_match);
138
139static struct platform_driver st_rng_driver = {
140 .driver = {
141 .name = "st-hwrandom",
142 .of_match_table = of_match_ptr(st_rng_match),
143 },
144 .probe = st_rng_probe,
145 .remove = st_rng_remove
146};
147
148module_platform_driver(st_rng_driver);
149
150MODULE_AUTHOR("Pankaj Dev <pankaj.dev@st.com>");
151MODULE_LICENSE("GPL v2");