1 /*
2  * RNG driver for Freescale RNGA
3  *
4  * Copyright 2008-2009 Freescale Semiconductor, Inc. All Rights Reserved.
5  * Author: Alan Carvalho de Assis <acassis@gmail.com>
6  */
7 
8 /*
9  * The code contained herein is licensed under the GNU General Public
10  * License. You may obtain a copy of the GNU General Public License
11  * Version 2 or later at the following locations:
12  *
13  * http://www.opensource.org/licenses/gpl-license.html
14  * http://www.gnu.org/copyleft/gpl.html
15  *
16  * This driver is based on other RNG drivers.
17  */
18 
19 #include <linux/module.h>
20 #include <linux/init.h>
21 #include <linux/kernel.h>
22 #include <linux/clk.h>
23 #include <linux/err.h>
24 #include <linux/ioport.h>
25 #include <linux/platform_device.h>
26 #include <linux/hw_random.h>
27 #include <linux/delay.h>
28 #include <linux/io.h>
29 
30 /* RNGA Registers */
31 #define RNGA_CONTROL			0x00
32 #define RNGA_STATUS			0x04
33 #define RNGA_ENTROPY			0x08
34 #define RNGA_OUTPUT_FIFO		0x0c
35 #define RNGA_MODE			0x10
36 #define RNGA_VERIFICATION_CONTROL	0x14
37 #define RNGA_OSC_CONTROL_COUNTER	0x18
38 #define RNGA_OSC1_COUNTER		0x1c
39 #define RNGA_OSC2_COUNTER		0x20
40 #define RNGA_OSC_COUNTER_STATUS		0x24
41 
42 /* RNGA Registers Range */
43 #define RNG_ADDR_RANGE			0x28
44 
45 /* RNGA Control Register */
46 #define RNGA_CONTROL_SLEEP		0x00000010
47 #define RNGA_CONTROL_CLEAR_INT		0x00000008
48 #define RNGA_CONTROL_MASK_INTS		0x00000004
49 #define RNGA_CONTROL_HIGH_ASSURANCE	0x00000002
50 #define RNGA_CONTROL_GO			0x00000001
51 
52 #define RNGA_STATUS_LEVEL_MASK		0x0000ff00
53 
54 /* RNGA Status Register */
55 #define RNGA_STATUS_OSC_DEAD		0x80000000
56 #define RNGA_STATUS_SLEEP		0x00000010
57 #define RNGA_STATUS_ERROR_INT		0x00000008
58 #define RNGA_STATUS_FIFO_UNDERFLOW	0x00000004
59 #define RNGA_STATUS_LAST_READ_STATUS	0x00000002
60 #define RNGA_STATUS_SECURITY_VIOLATION	0x00000001
61 
62 struct mxc_rng {
63 	struct device *dev;
64 	struct hwrng rng;
65 	void __iomem *mem;
66 	struct clk *clk;
67 };
68 
69 static int mxc_rnga_data_present(struct hwrng *rng, int wait)
70 {
71 	int i;
72 	struct mxc_rng *mxc_rng = container_of(rng, struct mxc_rng, rng);
73 
74 	for (i = 0; i < 20; i++) {
75 		/* how many random numbers are in FIFO? [0-16] */
76 		int level = (__raw_readl(mxc_rng->mem + RNGA_STATUS) &
77 				RNGA_STATUS_LEVEL_MASK) >> 8;
78 		if (level || !wait)
79 			return !!level;
80 		udelay(10);
81 	}
82 	return 0;
83 }
84 
85 static int mxc_rnga_data_read(struct hwrng *rng, u32 * data)
86 {
87 	int err;
88 	u32 ctrl;
89 	struct mxc_rng *mxc_rng = container_of(rng, struct mxc_rng, rng);
90 
91 	/* retrieve a random number from FIFO */
92 	*data = __raw_readl(mxc_rng->mem + RNGA_OUTPUT_FIFO);
93 
94 	/* some error while reading this random number? */
95 	err = __raw_readl(mxc_rng->mem + RNGA_STATUS) & RNGA_STATUS_ERROR_INT;
96 
97 	/* if error: clear error interrupt, but doesn't return random number */
98 	if (err) {
99 		dev_dbg(mxc_rng->dev, "Error while reading random number!\n");
100 		ctrl = __raw_readl(mxc_rng->mem + RNGA_CONTROL);
101 		__raw_writel(ctrl | RNGA_CONTROL_CLEAR_INT,
102 					mxc_rng->mem + RNGA_CONTROL);
103 		return 0;
104 	} else
105 		return 4;
106 }
107 
108 static int mxc_rnga_init(struct hwrng *rng)
109 {
110 	u32 ctrl, osc;
111 	struct mxc_rng *mxc_rng = container_of(rng, struct mxc_rng, rng);
112 
113 	/* wake up */
114 	ctrl = __raw_readl(mxc_rng->mem + RNGA_CONTROL);
115 	__raw_writel(ctrl & ~RNGA_CONTROL_SLEEP, mxc_rng->mem + RNGA_CONTROL);
116 
117 	/* verify if oscillator is working */
118 	osc = __raw_readl(mxc_rng->mem + RNGA_STATUS);
119 	if (osc & RNGA_STATUS_OSC_DEAD) {
120 		dev_err(mxc_rng->dev, "RNGA Oscillator is dead!\n");
121 		return -ENODEV;
122 	}
123 
124 	/* go running */
125 	ctrl = __raw_readl(mxc_rng->mem + RNGA_CONTROL);
126 	__raw_writel(ctrl | RNGA_CONTROL_GO, mxc_rng->mem + RNGA_CONTROL);
127 
128 	return 0;
129 }
130 
131 static void mxc_rnga_cleanup(struct hwrng *rng)
132 {
133 	u32 ctrl;
134 	struct mxc_rng *mxc_rng = container_of(rng, struct mxc_rng, rng);
135 
136 	ctrl = __raw_readl(mxc_rng->mem + RNGA_CONTROL);
137 
138 	/* stop rnga */
139 	__raw_writel(ctrl & ~RNGA_CONTROL_GO, mxc_rng->mem + RNGA_CONTROL);
140 }
141 
142 static int __init mxc_rnga_probe(struct platform_device *pdev)
143 {
144 	int err = -ENODEV;
145 	struct resource *res;
146 	struct mxc_rng *mxc_rng;
147 
148 	mxc_rng = devm_kzalloc(&pdev->dev, sizeof(struct mxc_rng),
149 					GFP_KERNEL);
150 	if (!mxc_rng)
151 		return -ENOMEM;
152 
153 	mxc_rng->dev = &pdev->dev;
154 	mxc_rng->rng.name = "mxc-rnga";
155 	mxc_rng->rng.init = mxc_rnga_init;
156 	mxc_rng->rng.cleanup = mxc_rnga_cleanup,
157 	mxc_rng->rng.data_present = mxc_rnga_data_present,
158 	mxc_rng->rng.data_read = mxc_rnga_data_read,
159 
160 	mxc_rng->clk = devm_clk_get(&pdev->dev, NULL);
161 	if (IS_ERR(mxc_rng->clk)) {
162 		dev_err(&pdev->dev, "Could not get rng_clk!\n");
163 		err = PTR_ERR(mxc_rng->clk);
164 		goto out;
165 	}
166 
167 	err = clk_prepare_enable(mxc_rng->clk);
168 	if (err)
169 		goto out;
170 
171 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
172 	mxc_rng->mem = devm_ioremap_resource(&pdev->dev, res);
173 	if (IS_ERR(mxc_rng->mem)) {
174 		err = PTR_ERR(mxc_rng->mem);
175 		goto err_ioremap;
176 	}
177 
178 	err = hwrng_register(&mxc_rng->rng);
179 	if (err) {
180 		dev_err(&pdev->dev, "MXC RNGA registering failed (%d)\n", err);
181 		goto err_ioremap;
182 	}
183 
184 	dev_info(&pdev->dev, "MXC RNGA Registered.\n");
185 
186 	return 0;
187 
188 err_ioremap:
189 	clk_disable_unprepare(mxc_rng->clk);
190 
191 out:
192 	return err;
193 }
194 
195 static int __exit mxc_rnga_remove(struct platform_device *pdev)
196 {
197 	struct mxc_rng *mxc_rng = platform_get_drvdata(pdev);
198 
199 	hwrng_unregister(&mxc_rng->rng);
200 
201 	clk_disable_unprepare(mxc_rng->clk);
202 
203 	return 0;
204 }
205 
206 static struct platform_driver mxc_rnga_driver = {
207 	.driver = {
208 		   .name = "mxc_rnga",
209 		   .owner = THIS_MODULE,
210 		   },
211 	.remove = __exit_p(mxc_rnga_remove),
212 };
213 
214 module_platform_driver_probe(mxc_rnga_driver, mxc_rnga_probe);
215 
216 MODULE_AUTHOR("Freescale Semiconductor, Inc.");
217 MODULE_DESCRIPTION("H/W RNGA driver for i.MX");
218 MODULE_LICENSE("GPL");
219