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 */
30static u32 (*omap3_rom_rng_call)(u32, u32, u32);
31
32static struct timer_list idle_timer;
33static int rng_idle;
34static struct clk *rng_clk;
35
36static 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
49static 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
74static int omap3_rom_rng_data_present(struct hwrng *rng, int wait)
75{
76	return 1;
77}
78
79static 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
89static 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
95static 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
119static 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
126static struct platform_driver omap3_rom_rng_driver = {
127	.driver = {
128		.name		= "omap3-rom-rng",
129	},
130	.probe		= omap3_rom_rng_probe,
131	.remove		= omap3_rom_rng_remove,
132};
133
134module_platform_driver(omap3_rom_rng_driver);
135
136MODULE_ALIAS("platform:omap3-rom-rng");
137MODULE_AUTHOR("Juha Yrjola");
138MODULE_AUTHOR("Pali Rohár <pali.rohar@gmail.com>");
139MODULE_LICENSE("GPL");
140