1 /*
2  * omap3-rom-rng.c - RNG driver for TI OMAP3 CPU family
3  *
4  * Copyright (C) 2009 Nokia Corporation
5  * Author: Juha Yrjola <juha.yrjola@solidboot.com>
6  *
7  * Copyright (C) 2013 Pali Rohár <pali.rohar@gmail.com>
8  *
9  * This file is licensed under  the terms of the GNU General Public
10  * License version 2. This program is licensed "as is" without any
11  * warranty of any kind, whether express or implied.
12  */
13 
14 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
15 
16 #include <linux/module.h>
17 #include <linux/init.h>
18 #include <linux/random.h>
19 #include <linux/hw_random.h>
20 #include <linux/timer.h>
21 #include <linux/clk.h>
22 #include <linux/err.h>
23 #include <linux/platform_device.h>
24 
25 #define RNG_RESET			0x01
26 #define RNG_GEN_PRNG_HW_INIT		0x02
27 #define RNG_GEN_HW			0x08
28 
29 /* param1: ptr, param2: count, param3: flag */
30 static u32 (*omap3_rom_rng_call)(u32, u32, u32);
31 
32 static struct timer_list idle_timer;
33 static int rng_idle;
34 static struct clk *rng_clk;
35 
36 static void omap3_rom_rng_idle(unsigned long data)
37 {
38 	int r;
39 
40 	r = omap3_rom_rng_call(0, 0, RNG_RESET);
41 	if (r != 0) {
42 		pr_err("reset failed: %d\n", r);
43 		return;
44 	}
45 	clk_disable_unprepare(rng_clk);
46 	rng_idle = 1;
47 }
48 
49 static int omap3_rom_rng_get_random(void *buf, unsigned int count)
50 {
51 	u32 r;
52 	u32 ptr;
53 
54 	del_timer_sync(&idle_timer);
55 	if (rng_idle) {
56 		clk_prepare_enable(rng_clk);
57 		r = omap3_rom_rng_call(0, 0, RNG_GEN_PRNG_HW_INIT);
58 		if (r != 0) {
59 			clk_disable_unprepare(rng_clk);
60 			pr_err("HW init failed: %d\n", r);
61 			return -EIO;
62 		}
63 		rng_idle = 0;
64 	}
65 
66 	ptr = virt_to_phys(buf);
67 	r = omap3_rom_rng_call(ptr, count, RNG_GEN_HW);
68 	mod_timer(&idle_timer, jiffies + msecs_to_jiffies(500));
69 	if (r != 0)
70 		return -EINVAL;
71 	return 0;
72 }
73 
74 static int omap3_rom_rng_data_present(struct hwrng *rng, int wait)
75 {
76 	return 1;
77 }
78 
79 static int omap3_rom_rng_data_read(struct hwrng *rng, u32 *data)
80 {
81 	int r;
82 
83 	r = omap3_rom_rng_get_random(data, 4);
84 	if (r < 0)
85 		return r;
86 	return 4;
87 }
88 
89 static struct hwrng omap3_rom_rng_ops = {
90 	.name		= "omap3-rom",
91 	.data_present	= omap3_rom_rng_data_present,
92 	.data_read	= omap3_rom_rng_data_read,
93 };
94 
95 static int omap3_rom_rng_probe(struct platform_device *pdev)
96 {
97 	pr_info("initializing\n");
98 
99 	omap3_rom_rng_call = pdev->dev.platform_data;
100 	if (!omap3_rom_rng_call) {
101 		pr_err("omap3_rom_rng_call is NULL\n");
102 		return -EINVAL;
103 	}
104 
105 	setup_timer(&idle_timer, omap3_rom_rng_idle, 0);
106 	rng_clk = devm_clk_get(&pdev->dev, "ick");
107 	if (IS_ERR(rng_clk)) {
108 		pr_err("unable to get RNG clock\n");
109 		return PTR_ERR(rng_clk);
110 	}
111 
112 	/* Leave the RNG in reset state. */
113 	clk_prepare_enable(rng_clk);
114 	omap3_rom_rng_idle(0);
115 
116 	return hwrng_register(&omap3_rom_rng_ops);
117 }
118 
119 static int omap3_rom_rng_remove(struct platform_device *pdev)
120 {
121 	hwrng_unregister(&omap3_rom_rng_ops);
122 	clk_disable_unprepare(rng_clk);
123 	return 0;
124 }
125 
126 static struct platform_driver omap3_rom_rng_driver = {
127 	.driver = {
128 		.name		= "omap3-rom-rng",
129 		.owner		= THIS_MODULE,
130 	},
131 	.probe		= omap3_rom_rng_probe,
132 	.remove		= omap3_rom_rng_remove,
133 };
134 
135 module_platform_driver(omap3_rom_rng_driver);
136 
137 MODULE_ALIAS("platform:omap3-rom-rng");
138 MODULE_AUTHOR("Juha Yrjola");
139 MODULE_AUTHOR("Pali Rohár <pali.rohar@gmail.com>");
140 MODULE_LICENSE("GPL");
141