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/platform_device.h>
17 #include <linux/slab.h>
18
19 #define RNGCON 0x04
20 #define TRNGEN BIT(8)
21 #define TRNGMOD BIT(11)
22 #define RNGSEED1 0x18
23 #define RNGSEED2 0x1C
24 #define RNGRCNT 0x20
25 #define RCNT_MASK 0x7F
26
27 struct pic32_rng {
28 void __iomem *base;
29 struct hwrng rng;
30 };
31
32 /*
33 * The TRNG can generate up to 24Mbps. This is a timeout that should be safe
34 * enough given the instructions in the loop and that the TRNG may not always
35 * be at maximum rate.
36 */
37 #define RNG_TIMEOUT 500
38
pic32_rng_init(struct hwrng * rng)39 static int pic32_rng_init(struct hwrng *rng)
40 {
41 struct pic32_rng *priv = container_of(rng, struct pic32_rng, rng);
42
43 /* enable TRNG in enhanced mode */
44 writel(TRNGEN | TRNGMOD, priv->base + RNGCON);
45 return 0;
46 }
47
pic32_rng_read(struct hwrng * rng,void * buf,size_t max,bool wait)48 static int pic32_rng_read(struct hwrng *rng, void *buf, size_t max,
49 bool wait)
50 {
51 struct pic32_rng *priv = container_of(rng, struct pic32_rng, rng);
52 u64 *data = buf;
53 u32 t;
54 unsigned int timeout = RNG_TIMEOUT;
55
56 do {
57 t = readl(priv->base + RNGRCNT) & RCNT_MASK;
58 if (t == 64) {
59 /* TRNG value comes through the seed registers */
60 *data = ((u64)readl(priv->base + RNGSEED2) << 32) +
61 readl(priv->base + RNGSEED1);
62 return 8;
63 }
64 } while (wait && --timeout);
65
66 return -EIO;
67 }
68
pic32_rng_cleanup(struct hwrng * rng)69 static void pic32_rng_cleanup(struct hwrng *rng)
70 {
71 struct pic32_rng *priv = container_of(rng, struct pic32_rng, rng);
72
73 writel(0, priv->base + RNGCON);
74 }
75
pic32_rng_probe(struct platform_device * pdev)76 static int pic32_rng_probe(struct platform_device *pdev)
77 {
78 struct pic32_rng *priv;
79 struct clk *clk;
80
81 priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
82 if (!priv)
83 return -ENOMEM;
84
85 priv->base = devm_platform_ioremap_resource(pdev, 0);
86 if (IS_ERR(priv->base))
87 return PTR_ERR(priv->base);
88
89 clk = devm_clk_get_enabled(&pdev->dev, NULL);
90 if (IS_ERR(clk))
91 return PTR_ERR(clk);
92
93 priv->rng.name = pdev->name;
94 priv->rng.init = pic32_rng_init;
95 priv->rng.read = pic32_rng_read;
96 priv->rng.cleanup = pic32_rng_cleanup;
97
98 return devm_hwrng_register(&pdev->dev, &priv->rng);
99 }
100
101 static const struct of_device_id pic32_rng_of_match[] __maybe_unused = {
102 { .compatible = "microchip,pic32mzda-rng", },
103 { /* sentinel */ }
104 };
105 MODULE_DEVICE_TABLE(of, pic32_rng_of_match);
106
107 static struct platform_driver pic32_rng_driver = {
108 .probe = pic32_rng_probe,
109 .driver = {
110 .name = "pic32-rng",
111 .of_match_table = pic32_rng_of_match,
112 },
113 };
114
115 module_platform_driver(pic32_rng_driver);
116
117 MODULE_LICENSE("GPL");
118 MODULE_AUTHOR("Joshua Henderson <joshua.henderson@microchip.com>");
119 MODULE_DESCRIPTION("Microchip PIC32 RNG Driver");
120