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
28struct 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
40static 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, addr: priv->base + RNGCON);
46 return 0;
47}
48
49static 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(addr: priv->base + RNGRCNT) & RCNT_MASK;
59 if (t == 64) {
60 /* TRNG value comes through the seed registers */
61 *data = ((u64)readl(addr: priv->base + RNGSEED2) << 32) +
62 readl(addr: priv->base + RNGSEED1);
63 return 8;
64 }
65 } while (wait && --timeout);
66
67 return -EIO;
68}
69
70static void pic32_rng_cleanup(struct hwrng *rng)
71{
72 struct pic32_rng *priv = container_of(rng, struct pic32_rng, rng);
73
74 writel(val: 0, addr: priv->base + RNGCON);
75}
76
77static int pic32_rng_probe(struct platform_device *pdev)
78{
79 struct pic32_rng *priv;
80 struct clk *clk;
81
82 priv = devm_kzalloc(dev: &pdev->dev, size: sizeof(*priv), GFP_KERNEL);
83 if (!priv)
84 return -ENOMEM;
85
86 priv->base = devm_platform_ioremap_resource(pdev, index: 0);
87 if (IS_ERR(ptr: priv->base))
88 return PTR_ERR(ptr: priv->base);
89
90 clk = devm_clk_get_enabled(dev: &pdev->dev, NULL);
91 if (IS_ERR(ptr: clk))
92 return PTR_ERR(ptr: 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(dev: &pdev->dev, rng: &priv->rng);
100}
101
102static const struct of_device_id pic32_rng_of_match[] __maybe_unused = {
103 { .compatible = "microchip,pic32mzda-rng", },
104 { /* sentinel */ }
105};
106MODULE_DEVICE_TABLE(of, pic32_rng_of_match);
107
108static 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
116module_platform_driver(pic32_rng_driver);
117
118MODULE_LICENSE("GPL");
119MODULE_AUTHOR("Joshua Henderson <joshua.henderson@microchip.com>");
120MODULE_DESCRIPTION("Microchip PIC32 RNG Driver");
121

source code of linux/drivers/char/hw_random/pic32-rng.c