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/workqueue.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 delayed_work idle_work;
33 static int rng_idle;
34 static struct clk *rng_clk;
35 
36 static void omap3_rom_rng_idle(struct work_struct *work)
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 	cancel_delayed_work_sync(&idle_work);
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 	schedule_delayed_work(&idle_work, msecs_to_jiffies(500));
69 	if (r != 0)
70 		return -EINVAL;
71 	return 0;
72 }
73 
74 static int omap3_rom_rng_read(struct hwrng *rng, void *data, size_t max, bool w)
75 {
76 	int r;
77 
78 	r = omap3_rom_rng_get_random(data, 4);
79 	if (r < 0)
80 		return r;
81 	return 4;
82 }
83 
84 static struct hwrng omap3_rom_rng_ops = {
85 	.name		= "omap3-rom",
86 	.read		= omap3_rom_rng_read,
87 };
88 
89 static int omap3_rom_rng_probe(struct platform_device *pdev)
90 {
91 	pr_info("initializing\n");
92 
93 	omap3_rom_rng_call = pdev->dev.platform_data;
94 	if (!omap3_rom_rng_call) {
95 		pr_err("omap3_rom_rng_call is NULL\n");
96 		return -EINVAL;
97 	}
98 
99 	INIT_DELAYED_WORK(&idle_work, omap3_rom_rng_idle);
100 	rng_clk = devm_clk_get(&pdev->dev, "ick");
101 	if (IS_ERR(rng_clk)) {
102 		pr_err("unable to get RNG clock\n");
103 		return PTR_ERR(rng_clk);
104 	}
105 
106 	/* Leave the RNG in reset state. */
107 	clk_prepare_enable(rng_clk);
108 	omap3_rom_rng_idle(0);
109 
110 	return hwrng_register(&omap3_rom_rng_ops);
111 }
112 
113 static int omap3_rom_rng_remove(struct platform_device *pdev)
114 {
115 	cancel_delayed_work_sync(&idle_work);
116 	hwrng_unregister(&omap3_rom_rng_ops);
117 	clk_disable_unprepare(rng_clk);
118 	return 0;
119 }
120 
121 static struct platform_driver omap3_rom_rng_driver = {
122 	.driver = {
123 		.name		= "omap3-rom-rng",
124 	},
125 	.probe		= omap3_rom_rng_probe,
126 	.remove		= omap3_rom_rng_remove,
127 };
128 
129 module_platform_driver(omap3_rom_rng_driver);
130 
131 MODULE_ALIAS("platform:omap3-rom-rng");
132 MODULE_AUTHOR("Juha Yrjola");
133 MODULE_AUTHOR("Pali Rohár <pali.rohar@gmail.com>");
134 MODULE_LICENSE("GPL");
135