1/*
2 * Generic PowerPC 44x RNG driver
3 *
4 * Copyright 2011 IBM Corporation
5 *
6 * This program is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU General Public License as published by the
8 * Free Software Foundation; version 2 of the License.
9 */
10
11#include <linux/module.h>
12#include <linux/kernel.h>
13#include <linux/platform_device.h>
14#include <linux/hw_random.h>
15#include <linux/delay.h>
16#include <linux/of_address.h>
17#include <linux/of_platform.h>
18#include <asm/io.h>
19
20#define PPC4XX_TRNG_DEV_CTRL 0x60080
21
22#define PPC4XX_TRNGE 0x00020000
23#define PPC4XX_TRNG_CTRL 0x0008
24#define PPC4XX_TRNG_CTRL_DALM 0x20
25#define PPC4XX_TRNG_STAT 0x0004
26#define PPC4XX_TRNG_STAT_B 0x1
27#define PPC4XX_TRNG_DATA 0x0000
28
29#define MODULE_NAME "ppc4xx_rng"
30
31static int ppc4xx_rng_data_present(struct hwrng *rng, int wait)
32{
33	void __iomem *rng_regs = (void __iomem *) rng->priv;
34	int busy, i, present = 0;
35
36	for (i = 0; i < 20; i++) {
37		busy = (in_le32(rng_regs + PPC4XX_TRNG_STAT) & PPC4XX_TRNG_STAT_B);
38		if (!busy || !wait) {
39			present = 1;
40			break;
41		}
42		udelay(10);
43	}
44	return present;
45}
46
47static int ppc4xx_rng_data_read(struct hwrng *rng, u32 *data)
48{
49	void __iomem *rng_regs = (void __iomem *) rng->priv;
50	*data = in_le32(rng_regs + PPC4XX_TRNG_DATA);
51	return 4;
52}
53
54static int ppc4xx_rng_enable(int enable)
55{
56	struct device_node *ctrl;
57	void __iomem *ctrl_reg;
58	int err = 0;
59	u32 val;
60
61	/* Find the main crypto device node and map it to turn the TRNG on */
62	ctrl = of_find_compatible_node(NULL, NULL, "amcc,ppc4xx-crypto");
63	if (!ctrl)
64		return -ENODEV;
65
66	ctrl_reg = of_iomap(ctrl, 0);
67	if (!ctrl_reg) {
68		err = -ENODEV;
69		goto out;
70	}
71
72	val = in_le32(ctrl_reg + PPC4XX_TRNG_DEV_CTRL);
73
74	if (enable)
75		val |= PPC4XX_TRNGE;
76	else
77		val = val & ~PPC4XX_TRNGE;
78
79	out_le32(ctrl_reg + PPC4XX_TRNG_DEV_CTRL, val);
80	iounmap(ctrl_reg);
81
82out:
83	of_node_put(ctrl);
84
85	return err;
86}
87
88static struct hwrng ppc4xx_rng = {
89	.name = MODULE_NAME,
90	.data_present = ppc4xx_rng_data_present,
91	.data_read = ppc4xx_rng_data_read,
92};
93
94static int ppc4xx_rng_probe(struct platform_device *dev)
95{
96	void __iomem *rng_regs;
97	int err = 0;
98
99	rng_regs = of_iomap(dev->dev.of_node, 0);
100	if (!rng_regs)
101		return -ENODEV;
102
103	err = ppc4xx_rng_enable(1);
104	if (err)
105		return err;
106
107	out_le32(rng_regs + PPC4XX_TRNG_CTRL, PPC4XX_TRNG_CTRL_DALM);
108	ppc4xx_rng.priv = (unsigned long) rng_regs;
109
110	err = hwrng_register(&ppc4xx_rng);
111
112	return err;
113}
114
115static int ppc4xx_rng_remove(struct platform_device *dev)
116{
117	void __iomem *rng_regs = (void __iomem *) ppc4xx_rng.priv;
118
119	hwrng_unregister(&ppc4xx_rng);
120	ppc4xx_rng_enable(0);
121	iounmap(rng_regs);
122
123	return 0;
124}
125
126static const struct of_device_id ppc4xx_rng_match[] = {
127	{ .compatible = "ppc4xx-rng", },
128	{ .compatible = "amcc,ppc460ex-rng", },
129	{ .compatible = "amcc,ppc440epx-rng", },
130	{},
131};
132
133static struct platform_driver ppc4xx_rng_driver = {
134	.driver = {
135		.name = MODULE_NAME,
136		.of_match_table = ppc4xx_rng_match,
137	},
138	.probe = ppc4xx_rng_probe,
139	.remove = ppc4xx_rng_remove,
140};
141
142module_platform_driver(ppc4xx_rng_driver);
143
144MODULE_LICENSE("GPL");
145MODULE_AUTHOR("Josh Boyer <jwboyer@linux.vnet.ibm.com>");
146MODULE_DESCRIPTION("HW RNG driver for PPC 4xx processors");
147