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
36struct 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
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(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
70static 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 = hwrng_register(&priv->rng);
100	if (ret)
101		goto err_register;
102
103	platform_set_drvdata(pdev, priv);
104
105	return 0;
106
107err_register:
108	clk_disable_unprepare(priv->clk);
109	return ret;
110}
111
112static int pic32_rng_remove(struct platform_device *pdev)
113{
114	struct pic32_rng *rng = platform_get_drvdata(pdev);
115
116	hwrng_unregister(&rng->rng);
117	writel(0, rng->base + RNGCON);
118	clk_disable_unprepare(rng->clk);
119	return 0;
120}
121
122static const struct of_device_id pic32_rng_of_match[] __maybe_unused = {
123	{ .compatible	= "microchip,pic32mzda-rng", },
124	{ /* sentinel */ }
125};
126MODULE_DEVICE_TABLE(of, pic32_rng_of_match);
127
128static struct platform_driver pic32_rng_driver = {
129	.probe		= pic32_rng_probe,
130	.remove		= pic32_rng_remove,
131	.driver		= {
132		.name	= "pic32-rng",
133		.of_match_table = of_match_ptr(pic32_rng_of_match),
134	},
135};
136
137module_platform_driver(pic32_rng_driver);
138
139MODULE_LICENSE("GPL");
140MODULE_AUTHOR("Joshua Henderson <joshua.henderson@microchip.com>");
141MODULE_DESCRIPTION("Microchip PIC32 RNG Driver");
142