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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * ST Random Number Generator Driver ST's Platforms
4 *
5 * Author: Pankaj Dev: <pankaj.dev@st.com>
6 * Lee Jones <lee.jones@linaro.org>
7 *
8 * Copyright (C) 2015 STMicroelectronics (R&D) Limited
9 */
10
11#include <linux/clk.h>
12#include <linux/delay.h>
13#include <linux/hw_random.h>
14#include <linux/io.h>
15#include <linux/kernel.h>
16#include <linux/module.h>
17#include <linux/of.h>
18#include <linux/platform_device.h>
19#include <linux/slab.h>
20
21/* Registers */
22#define ST_RNG_STATUS_REG 0x20
23#define ST_RNG_DATA_REG 0x24
24
25/* Registers fields */
26#define ST_RNG_STATUS_BAD_SEQUENCE BIT(0)
27#define ST_RNG_STATUS_BAD_ALTERNANCE BIT(1)
28#define ST_RNG_STATUS_FIFO_FULL BIT(5)
29
30#define ST_RNG_SAMPLE_SIZE 2 /* 2 Byte (16bit) samples */
31#define ST_RNG_FIFO_DEPTH 4
32#define ST_RNG_FIFO_SIZE (ST_RNG_FIFO_DEPTH * ST_RNG_SAMPLE_SIZE)
33
34/*
35 * Samples are documented to be available every 0.667us, so in theory
36 * the 4 sample deep FIFO should take 2.668us to fill. However, during
37 * thorough testing, it became apparent that filling the FIFO actually
38 * takes closer to 12us. We then multiply by 2 in order to account for
39 * the lack of udelay()'s reliability, suggested by Russell King.
40 */
41#define ST_RNG_FILL_FIFO_TIMEOUT (12 * 2)
42
43struct st_rng_data {
44 void __iomem *base;
45 struct hwrng ops;
46};
47
48static int st_rng_read(struct hwrng *rng, void *data, size_t max, bool wait)
49{
50 struct st_rng_data *ddata = (struct st_rng_data *)rng->priv;
51 u32 status;
52 int i;
53
54 /* Wait until FIFO is full - max 4uS*/
55 for (i = 0; i < ST_RNG_FILL_FIFO_TIMEOUT; i++) {
56 status = readl_relaxed(ddata->base + ST_RNG_STATUS_REG);
57 if (status & ST_RNG_STATUS_FIFO_FULL)
58 break;
59 udelay(1);
60 }
61
62 if (i == ST_RNG_FILL_FIFO_TIMEOUT)
63 return 0;
64
65 for (i = 0; i < ST_RNG_FIFO_SIZE && i < max; i += 2)
66 *(u16 *)(data + i) =
67 readl_relaxed(ddata->base + ST_RNG_DATA_REG);
68
69 return i; /* No of bytes read */
70}
71
72static int st_rng_probe(struct platform_device *pdev)
73{
74 struct st_rng_data *ddata;
75 struct clk *clk;
76 void __iomem *base;
77 int ret;
78
79 ddata = devm_kzalloc(&pdev->dev, sizeof(*ddata), GFP_KERNEL);
80 if (!ddata)
81 return -ENOMEM;
82
83 base = devm_platform_ioremap_resource(pdev, 0);
84 if (IS_ERR(base))
85 return PTR_ERR(base);
86
87 clk = devm_clk_get_enabled(&pdev->dev, NULL);
88 if (IS_ERR(clk))
89 return PTR_ERR(clk);
90
91 ddata->ops.priv = (unsigned long)ddata;
92 ddata->ops.read = st_rng_read;
93 ddata->ops.name = pdev->name;
94 ddata->base = base;
95
96 ret = devm_hwrng_register(&pdev->dev, &ddata->ops);
97 if (ret) {
98 dev_err(&pdev->dev, "Failed to register HW RNG\n");
99 return ret;
100 }
101
102 dev_info(&pdev->dev, "Successfully registered HW RNG\n");
103
104 return 0;
105}
106
107static const struct of_device_id st_rng_match[] __maybe_unused = {
108 { .compatible = "st,rng" },
109 {},
110};
111MODULE_DEVICE_TABLE(of, st_rng_match);
112
113static struct platform_driver st_rng_driver = {
114 .driver = {
115 .name = "st-hwrandom",
116 .of_match_table = of_match_ptr(st_rng_match),
117 },
118 .probe = st_rng_probe,
119};
120
121module_platform_driver(st_rng_driver);
122
123MODULE_AUTHOR("Pankaj Dev <pankaj.dev@st.com>");
124MODULE_DESCRIPTION("ST Microelectronics HW Random Number Generator");
125MODULE_LICENSE("GPL v2");
1/*
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
32#define ST_RNG_SAMPLE_SIZE 2 /* 2 Byte (16bit) samples */
33#define ST_RNG_FIFO_DEPTH 4
34#define ST_RNG_FIFO_SIZE (ST_RNG_FIFO_DEPTH * ST_RNG_SAMPLE_SIZE)
35
36/*
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)
44
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 /* Wait until FIFO is full - max 4uS*/
58 for (i = 0; i < ST_RNG_FILL_FIFO_TIMEOUT; i++) {
59 status = readl_relaxed(ddata->base + ST_RNG_STATUS_REG);
60 if (status & ST_RNG_STATUS_FIFO_FULL)
61 break;
62 udelay(1);
63 }
64
65 if (i == ST_RNG_FILL_FIFO_TIMEOUT)
66 return 0;
67
68 for (i = 0; i < ST_RNG_FIFO_SIZE && i < max; i += 2)
69 *(u16 *)(data + i) =
70 readl_relaxed(ddata->base + ST_RNG_DATA_REG);
71
72 return i; /* No of bytes read */
73}
74
75static int st_rng_probe(struct platform_device *pdev)
76{
77 struct st_rng_data *ddata;
78 struct resource *res;
79 struct clk *clk;
80 void __iomem *base;
81 int ret;
82
83 ddata = devm_kzalloc(&pdev->dev, sizeof(*ddata), GFP_KERNEL);
84 if (!ddata)
85 return -ENOMEM;
86
87 res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
88 base = devm_ioremap_resource(&pdev->dev, res);
89 if (IS_ERR(base))
90 return PTR_ERR(base);
91
92 clk = devm_clk_get(&pdev->dev, NULL);
93 if (IS_ERR(clk))
94 return PTR_ERR(clk);
95
96 ret = clk_prepare_enable(clk);
97 if (ret)
98 return ret;
99
100 ddata->ops.priv = (unsigned long)ddata;
101 ddata->ops.read = st_rng_read;
102 ddata->ops.name = pdev->name;
103 ddata->base = base;
104 ddata->clk = clk;
105
106 dev_set_drvdata(&pdev->dev, ddata);
107
108 ret = hwrng_register(&ddata->ops);
109 if (ret) {
110 dev_err(&pdev->dev, "Failed to register HW RNG\n");
111 clk_disable_unprepare(clk);
112 return ret;
113 }
114
115 dev_info(&pdev->dev, "Successfully registered HW RNG\n");
116
117 return 0;
118}
119
120static int st_rng_remove(struct platform_device *pdev)
121{
122 struct st_rng_data *ddata = dev_get_drvdata(&pdev->dev);
123
124 hwrng_unregister(&ddata->ops);
125
126 clk_disable_unprepare(ddata->clk);
127
128 return 0;
129}
130
131static const struct of_device_id st_rng_match[] = {
132 { .compatible = "st,rng" },
133 {},
134};
135MODULE_DEVICE_TABLE(of, st_rng_match);
136
137static struct platform_driver st_rng_driver = {
138 .driver = {
139 .name = "st-hwrandom",
140 .of_match_table = of_match_ptr(st_rng_match),
141 },
142 .probe = st_rng_probe,
143 .remove = st_rng_remove
144};
145
146module_platform_driver(st_rng_driver);
147
148MODULE_AUTHOR("Pankaj Dev <pankaj.dev@st.com>");
149MODULE_LICENSE("GPL v2");