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/mod_devicetable.h>
16 #include <linux/module.h>
17 #include <linux/platform_device.h>
18 #include <linux/slab.h>
19
20 #define RNGCON 0x04
21 #define TRNGEN BIT(8)
22 #define TRNGMOD BIT(11)
23 #define RNGSEED1 0x18
24 #define RNGSEED2 0x1C
25 #define RNGRCNT 0x20
26 #define RCNT_MASK 0x7F
27
28 struct pic32_rng {
29 void __iomem *base;
30 struct hwrng rng;
31 };
32
33 /*
34 * The TRNG can generate up to 24Mbps. This is a timeout that should be safe
35 * enough given the instructions in the loop and that the TRNG may not always
36 * be at maximum rate.
37 */
38 #define RNG_TIMEOUT 500
39
pic32_rng_init(struct hwrng * rng)40 static int pic32_rng_init(struct hwrng *rng)
41 {
42 struct pic32_rng *priv = container_of(rng, struct pic32_rng, rng);
43
44 /* enable TRNG in enhanced mode */
45 writel(TRNGEN | TRNGMOD, priv->base + RNGCON);
46 return 0;
47 }
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_cleanup(struct hwrng * rng)70 static void pic32_rng_cleanup(struct hwrng *rng)
71 {
72 struct pic32_rng *priv = container_of(rng, struct pic32_rng, rng);
73
74 writel(0, priv->base + RNGCON);
75 }
76
pic32_rng_probe(struct platform_device * pdev)77 static int pic32_rng_probe(struct platform_device *pdev)
78 {
79 struct pic32_rng *priv;
80 struct clk *clk;
81
82 priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
83 if (!priv)
84 return -ENOMEM;
85
86 priv->base = devm_platform_ioremap_resource(pdev, 0);
87 if (IS_ERR(priv->base))
88 return PTR_ERR(priv->base);
89
90 clk = devm_clk_get_enabled(&pdev->dev, NULL);
91 if (IS_ERR(clk))
92 return PTR_ERR(clk);
93
94 priv->rng.name = pdev->name;
95 priv->rng.init = pic32_rng_init;
96 priv->rng.read = pic32_rng_read;
97 priv->rng.cleanup = pic32_rng_cleanup;
98
99 return devm_hwrng_register(&pdev->dev, &priv->rng);
100 }
101
102 static const struct of_device_id pic32_rng_of_match[] __maybe_unused = {
103 { .compatible = "microchip,pic32mzda-rng", },
104 { /* sentinel */ }
105 };
106 MODULE_DEVICE_TABLE(of, pic32_rng_of_match);
107
108 static struct platform_driver pic32_rng_driver = {
109 .probe = pic32_rng_probe,
110 .driver = {
111 .name = "pic32-rng",
112 .of_match_table = pic32_rng_of_match,
113 },
114 };
115
116 module_platform_driver(pic32_rng_driver);
117
118 MODULE_LICENSE("GPL");
119 MODULE_AUTHOR("Joshua Henderson <joshua.henderson@microchip.com>");
120 MODULE_DESCRIPTION("Microchip PIC32 RNG Driver");
121