1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * PIC32 RNG driver
4 *
5 * Joshua Henderson <joshua.henderson@microchip.com>
6 * Copyright (C) 2016 Microchip Technology Inc. All rights reserved.
7 */
8
9 #include <linux/clk.h>
10 #include <linux/clkdev.h>
11 #include <linux/err.h>
12 #include <linux/hw_random.h>
13 #include <linux/io.h>
14 #include <linux/kernel.h>
15 #include <linux/module.h>
16 #include <linux/of.h>
17 #include <linux/of_device.h>
18 #include <linux/platform_device.h>
19 #include <linux/slab.h>
20
21 #define RNGCON 0x04
22 #define TRNGEN BIT(8)
23 #define PRNGEN BIT(9)
24 #define PRNGCONT BIT(10)
25 #define TRNGMOD BIT(11)
26 #define SEEDLOAD BIT(12)
27 #define RNGPOLY1 0x08
28 #define RNGPOLY2 0x0C
29 #define RNGNUMGEN1 0x10
30 #define RNGNUMGEN2 0x14
31 #define RNGSEED1 0x18
32 #define RNGSEED2 0x1C
33 #define RNGRCNT 0x20
34 #define RCNT_MASK 0x7F
35
36 struct pic32_rng {
37 void __iomem *base;
38 struct hwrng rng;
39 struct clk *clk;
40 };
41
42 /*
43 * The TRNG can generate up to 24Mbps. This is a timeout that should be safe
44 * enough given the instructions in the loop and that the TRNG may not always
45 * be at maximum rate.
46 */
47 #define RNG_TIMEOUT 500
48
pic32_rng_read(struct hwrng * rng,void * buf,size_t max,bool wait)49 static int pic32_rng_read(struct hwrng *rng, void *buf, size_t max,
50 bool wait)
51 {
52 struct pic32_rng *priv = container_of(rng, struct pic32_rng, rng);
53 u64 *data = buf;
54 u32 t;
55 unsigned int timeout = RNG_TIMEOUT;
56
57 do {
58 t = readl(priv->base + RNGRCNT) & RCNT_MASK;
59 if (t == 64) {
60 /* TRNG value comes through the seed registers */
61 *data = ((u64)readl(priv->base + RNGSEED2) << 32) +
62 readl(priv->base + RNGSEED1);
63 return 8;
64 }
65 } while (wait && --timeout);
66
67 return -EIO;
68 }
69
pic32_rng_probe(struct platform_device * pdev)70 static int pic32_rng_probe(struct platform_device *pdev)
71 {
72 struct pic32_rng *priv;
73 u32 v;
74 int ret;
75
76 priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
77 if (!priv)
78 return -ENOMEM;
79
80 priv->base = devm_platform_ioremap_resource(pdev, 0);
81 if (IS_ERR(priv->base))
82 return PTR_ERR(priv->base);
83
84 priv->clk = devm_clk_get(&pdev->dev, NULL);
85 if (IS_ERR(priv->clk))
86 return PTR_ERR(priv->clk);
87
88 ret = clk_prepare_enable(priv->clk);
89 if (ret)
90 return ret;
91
92 /* enable TRNG in enhanced mode */
93 v = TRNGEN | TRNGMOD;
94 writel(v, priv->base + RNGCON);
95
96 priv->rng.name = pdev->name;
97 priv->rng.read = pic32_rng_read;
98
99 ret = devm_hwrng_register(&pdev->dev, &priv->rng);
100 if (ret)
101 goto err_register;
102
103 platform_set_drvdata(pdev, priv);
104
105 return 0;
106
107 err_register:
108 clk_disable_unprepare(priv->clk);
109 return ret;
110 }
111
pic32_rng_remove(struct platform_device * pdev)112 static int pic32_rng_remove(struct platform_device *pdev)
113 {
114 struct pic32_rng *rng = platform_get_drvdata(pdev);
115
116 writel(0, rng->base + RNGCON);
117 clk_disable_unprepare(rng->clk);
118 return 0;
119 }
120
121 static const struct of_device_id pic32_rng_of_match[] __maybe_unused = {
122 { .compatible = "microchip,pic32mzda-rng", },
123 { /* sentinel */ }
124 };
125 MODULE_DEVICE_TABLE(of, pic32_rng_of_match);
126
127 static struct platform_driver pic32_rng_driver = {
128 .probe = pic32_rng_probe,
129 .remove = pic32_rng_remove,
130 .driver = {
131 .name = "pic32-rng",
132 .of_match_table = of_match_ptr(pic32_rng_of_match),
133 },
134 };
135
136 module_platform_driver(pic32_rng_driver);
137
138 MODULE_LICENSE("GPL");
139 MODULE_AUTHOR("Joshua Henderson <joshua.henderson@microchip.com>");
140 MODULE_DESCRIPTION("Microchip PIC32 RNG Driver");
141