1 /*
2 * Copyright (c) 2011-2013, The Linux Foundation. All rights reserved.
3 *
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License version 2 and
6 * only version 2 as published by the Free Software Foundation.
7 *
8 * This program is distributed in the hope that it will be useful,
9 * but WITHOUT ANY WARRANTY; without even the implied warranty of
10 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
11 * GNU General Public License for more details.
12 *
13 */
14 #include <linux/clk.h>
15 #include <linux/err.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
22 /* Device specific register offsets */
23 #define PRNG_DATA_OUT 0x0000
24 #define PRNG_STATUS 0x0004
25 #define PRNG_LFSR_CFG 0x0100
26 #define PRNG_CONFIG 0x0104
27
28 /* Device specific register masks and config values */
29 #define PRNG_LFSR_CFG_MASK 0x0000ffff
30 #define PRNG_LFSR_CFG_CLOCKS 0x0000dddd
31 #define PRNG_CONFIG_HW_ENABLE BIT(1)
32 #define PRNG_STATUS_DATA_AVAIL BIT(0)
33
34 #define MAX_HW_FIFO_DEPTH 16
35 #define MAX_HW_FIFO_SIZE (MAX_HW_FIFO_DEPTH * 4)
36 #define WORD_SZ 4
37
38 struct msm_rng {
39 void __iomem *base;
40 struct clk *clk;
41 struct hwrng hwrng;
42 };
43
44 #define to_msm_rng(p) container_of(p, struct msm_rng, hwrng)
45
msm_rng_enable(struct hwrng * hwrng,int enable)46 static int msm_rng_enable(struct hwrng *hwrng, int enable)
47 {
48 struct msm_rng *rng = to_msm_rng(hwrng);
49 u32 val;
50 int ret;
51
52 ret = clk_prepare_enable(rng->clk);
53 if (ret)
54 return ret;
55
56 if (enable) {
57 /* Enable PRNG only if it is not already enabled */
58 val = readl_relaxed(rng->base + PRNG_CONFIG);
59 if (val & PRNG_CONFIG_HW_ENABLE)
60 goto already_enabled;
61
62 val = readl_relaxed(rng->base + PRNG_LFSR_CFG);
63 val &= ~PRNG_LFSR_CFG_MASK;
64 val |= PRNG_LFSR_CFG_CLOCKS;
65 writel(val, rng->base + PRNG_LFSR_CFG);
66
67 val = readl_relaxed(rng->base + PRNG_CONFIG);
68 val |= PRNG_CONFIG_HW_ENABLE;
69 writel(val, rng->base + PRNG_CONFIG);
70 } else {
71 val = readl_relaxed(rng->base + PRNG_CONFIG);
72 val &= ~PRNG_CONFIG_HW_ENABLE;
73 writel(val, rng->base + PRNG_CONFIG);
74 }
75
76 already_enabled:
77 clk_disable_unprepare(rng->clk);
78 return 0;
79 }
80
msm_rng_read(struct hwrng * hwrng,void * data,size_t max,bool wait)81 static int msm_rng_read(struct hwrng *hwrng, void *data, size_t max, bool wait)
82 {
83 struct msm_rng *rng = to_msm_rng(hwrng);
84 size_t currsize = 0;
85 u32 *retdata = data;
86 size_t maxsize;
87 int ret;
88 u32 val;
89
90 /* calculate max size bytes to transfer back to caller */
91 maxsize = min_t(size_t, MAX_HW_FIFO_SIZE, max);
92
93 ret = clk_prepare_enable(rng->clk);
94 if (ret)
95 return ret;
96
97 /* read random data from hardware */
98 do {
99 val = readl_relaxed(rng->base + PRNG_STATUS);
100 if (!(val & PRNG_STATUS_DATA_AVAIL))
101 break;
102
103 val = readl_relaxed(rng->base + PRNG_DATA_OUT);
104 if (!val)
105 break;
106
107 *retdata++ = val;
108 currsize += WORD_SZ;
109
110 /* make sure we stay on 32bit boundary */
111 if ((maxsize - currsize) < WORD_SZ)
112 break;
113 } while (currsize < maxsize);
114
115 clk_disable_unprepare(rng->clk);
116
117 return currsize;
118 }
119
msm_rng_init(struct hwrng * hwrng)120 static int msm_rng_init(struct hwrng *hwrng)
121 {
122 return msm_rng_enable(hwrng, 1);
123 }
124
msm_rng_cleanup(struct hwrng * hwrng)125 static void msm_rng_cleanup(struct hwrng *hwrng)
126 {
127 msm_rng_enable(hwrng, 0);
128 }
129
msm_rng_probe(struct platform_device * pdev)130 static int msm_rng_probe(struct platform_device *pdev)
131 {
132 struct resource *res;
133 struct msm_rng *rng;
134 int ret;
135
136 rng = devm_kzalloc(&pdev->dev, sizeof(*rng), GFP_KERNEL);
137 if (!rng)
138 return -ENOMEM;
139
140 platform_set_drvdata(pdev, rng);
141
142 res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
143 rng->base = devm_ioremap_resource(&pdev->dev, res);
144 if (IS_ERR(rng->base))
145 return PTR_ERR(rng->base);
146
147 rng->clk = devm_clk_get(&pdev->dev, "core");
148 if (IS_ERR(rng->clk))
149 return PTR_ERR(rng->clk);
150
151 rng->hwrng.name = KBUILD_MODNAME,
152 rng->hwrng.init = msm_rng_init,
153 rng->hwrng.cleanup = msm_rng_cleanup,
154 rng->hwrng.read = msm_rng_read,
155
156 ret = devm_hwrng_register(&pdev->dev, &rng->hwrng);
157 if (ret) {
158 dev_err(&pdev->dev, "failed to register hwrng\n");
159 return ret;
160 }
161
162 return 0;
163 }
164
165 static const struct of_device_id msm_rng_of_match[] = {
166 { .compatible = "qcom,prng", },
167 {}
168 };
169 MODULE_DEVICE_TABLE(of, msm_rng_of_match);
170
171 static struct platform_driver msm_rng_driver = {
172 .probe = msm_rng_probe,
173 .driver = {
174 .name = KBUILD_MODNAME,
175 .of_match_table = of_match_ptr(msm_rng_of_match),
176 }
177 };
178 module_platform_driver(msm_rng_driver);
179
180 MODULE_ALIAS("platform:" KBUILD_MODNAME);
181 MODULE_AUTHOR("The Linux Foundation");
182 MODULE_DESCRIPTION("Qualcomm MSM random number generator driver");
183 MODULE_LICENSE("GPL v2");
184