1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * RNG driver for Freescale RNGA
4 *
5 * Copyright 2008-2009 Freescale Semiconductor, Inc. All Rights Reserved.
6 * Author: Alan Carvalho de Assis <acassis@gmail.com>
7 */
8
9/*
10 *
11 * This driver is based on other RNG drivers.
12 */
13
14#include <linux/clk.h>
15#include <linux/delay.h>
16#include <linux/hw_random.h>
17#include <linux/io.h>
18#include <linux/module.h>
19#include <linux/of.h>
20#include <linux/platform_device.h>
21
22/* RNGA Registers */
23#define RNGA_CONTROL			0x00
24#define RNGA_STATUS			0x04
25#define RNGA_ENTROPY			0x08
26#define RNGA_OUTPUT_FIFO		0x0c
27#define RNGA_MODE			0x10
28#define RNGA_VERIFICATION_CONTROL	0x14
29#define RNGA_OSC_CONTROL_COUNTER	0x18
30#define RNGA_OSC1_COUNTER		0x1c
31#define RNGA_OSC2_COUNTER		0x20
32#define RNGA_OSC_COUNTER_STATUS		0x24
33
34/* RNGA Registers Range */
35#define RNG_ADDR_RANGE			0x28
36
37/* RNGA Control Register */
38#define RNGA_CONTROL_SLEEP		0x00000010
39#define RNGA_CONTROL_CLEAR_INT		0x00000008
40#define RNGA_CONTROL_MASK_INTS		0x00000004
41#define RNGA_CONTROL_HIGH_ASSURANCE	0x00000002
42#define RNGA_CONTROL_GO			0x00000001
43
44#define RNGA_STATUS_LEVEL_MASK		0x0000ff00
45
46/* RNGA Status Register */
47#define RNGA_STATUS_OSC_DEAD		0x80000000
48#define RNGA_STATUS_SLEEP		0x00000010
49#define RNGA_STATUS_ERROR_INT		0x00000008
50#define RNGA_STATUS_FIFO_UNDERFLOW	0x00000004
51#define RNGA_STATUS_LAST_READ_STATUS	0x00000002
52#define RNGA_STATUS_SECURITY_VIOLATION	0x00000001
53
54struct mxc_rng {
55	struct device *dev;
56	struct hwrng rng;
57	void __iomem *mem;
58	struct clk *clk;
59};
60
61static int mxc_rnga_data_present(struct hwrng *rng, int wait)
62{
63	int i;
64	struct mxc_rng *mxc_rng = container_of(rng, struct mxc_rng, rng);
65
66	for (i = 0; i < 20; i++) {
67		/* how many random numbers are in FIFO? [0-16] */
68		int level = (__raw_readl(mxc_rng->mem + RNGA_STATUS) &
69				RNGA_STATUS_LEVEL_MASK) >> 8;
70		if (level || !wait)
71			return !!level;
72		udelay(10);
73	}
74	return 0;
75}
76
77static int mxc_rnga_data_read(struct hwrng *rng, u32 * data)
78{
79	int err;
80	u32 ctrl;
81	struct mxc_rng *mxc_rng = container_of(rng, struct mxc_rng, rng);
82
83	/* retrieve a random number from FIFO */
84	*data = __raw_readl(mxc_rng->mem + RNGA_OUTPUT_FIFO);
85
86	/* some error while reading this random number? */
87	err = __raw_readl(mxc_rng->mem + RNGA_STATUS) & RNGA_STATUS_ERROR_INT;
88
89	/* if error: clear error interrupt, but doesn't return random number */
90	if (err) {
91		dev_dbg(mxc_rng->dev, "Error while reading random number!\n");
92		ctrl = __raw_readl(mxc_rng->mem + RNGA_CONTROL);
93		__raw_writel(ctrl | RNGA_CONTROL_CLEAR_INT,
94					mxc_rng->mem + RNGA_CONTROL);
95		return 0;
96	} else
97		return 4;
98}
99
100static int mxc_rnga_init(struct hwrng *rng)
101{
102	u32 ctrl, osc;
103	struct mxc_rng *mxc_rng = container_of(rng, struct mxc_rng, rng);
104
105	/* wake up */
106	ctrl = __raw_readl(mxc_rng->mem + RNGA_CONTROL);
107	__raw_writel(ctrl & ~RNGA_CONTROL_SLEEP, mxc_rng->mem + RNGA_CONTROL);
108
109	/* verify if oscillator is working */
110	osc = __raw_readl(mxc_rng->mem + RNGA_STATUS);
111	if (osc & RNGA_STATUS_OSC_DEAD) {
112		dev_err(mxc_rng->dev, "RNGA Oscillator is dead!\n");
113		return -ENODEV;
114	}
115
116	/* go running */
117	ctrl = __raw_readl(mxc_rng->mem + RNGA_CONTROL);
118	__raw_writel(ctrl | RNGA_CONTROL_GO, mxc_rng->mem + RNGA_CONTROL);
119
120	return 0;
121}
122
123static void mxc_rnga_cleanup(struct hwrng *rng)
124{
125	u32 ctrl;
126	struct mxc_rng *mxc_rng = container_of(rng, struct mxc_rng, rng);
127
128	ctrl = __raw_readl(mxc_rng->mem + RNGA_CONTROL);
129
130	/* stop rnga */
131	__raw_writel(ctrl & ~RNGA_CONTROL_GO, mxc_rng->mem + RNGA_CONTROL);
132}
133
134static int __init mxc_rnga_probe(struct platform_device *pdev)
135{
136	int err;
137	struct mxc_rng *mxc_rng;
138
139	mxc_rng = devm_kzalloc(&pdev->dev, sizeof(*mxc_rng), GFP_KERNEL);
140	if (!mxc_rng)
141		return -ENOMEM;
142
143	mxc_rng->dev = &pdev->dev;
144	mxc_rng->rng.name = "mxc-rnga";
145	mxc_rng->rng.init = mxc_rnga_init;
146	mxc_rng->rng.cleanup = mxc_rnga_cleanup;
147	mxc_rng->rng.data_present = mxc_rnga_data_present;
148	mxc_rng->rng.data_read = mxc_rnga_data_read;
149
150	mxc_rng->clk = devm_clk_get(&pdev->dev, NULL);
151	if (IS_ERR(mxc_rng->clk)) {
152		dev_err(&pdev->dev, "Could not get rng_clk!\n");
153		return PTR_ERR(mxc_rng->clk);
154	}
155
156	err = clk_prepare_enable(mxc_rng->clk);
157	if (err)
158		return err;
159
160	mxc_rng->mem = devm_platform_ioremap_resource(pdev, 0);
161	if (IS_ERR(mxc_rng->mem)) {
162		err = PTR_ERR(mxc_rng->mem);
163		goto err_ioremap;
164	}
165
166	err = hwrng_register(&mxc_rng->rng);
167	if (err) {
168		dev_err(&pdev->dev, "MXC RNGA registering failed (%d)\n", err);
169		goto err_ioremap;
170	}
171
172	return 0;
173
174err_ioremap:
175	clk_disable_unprepare(mxc_rng->clk);
176	return err;
177}
178
179static int __exit mxc_rnga_remove(struct platform_device *pdev)
180{
181	struct mxc_rng *mxc_rng = platform_get_drvdata(pdev);
182
183	hwrng_unregister(&mxc_rng->rng);
184
185	clk_disable_unprepare(mxc_rng->clk);
186
187	return 0;
188}
189
190static const struct of_device_id mxc_rnga_of_match[] = {
191	{ .compatible = "fsl,imx21-rnga", },
192	{ .compatible = "fsl,imx31-rnga", },
193	{ /* sentinel */ },
194};
195MODULE_DEVICE_TABLE(of, mxc_rnga_of_match);
196
197static struct platform_driver mxc_rnga_driver = {
198	.driver = {
199		.name = "mxc_rnga",
200		.of_match_table = mxc_rnga_of_match,
201	},
202	.remove = __exit_p(mxc_rnga_remove),
203};
204
205module_platform_driver_probe(mxc_rnga_driver, mxc_rnga_probe);
206
207MODULE_AUTHOR("Freescale Semiconductor, Inc.");
208MODULE_DESCRIPTION("H/W RNGA driver for i.MX");
209MODULE_LICENSE("GPL");
210