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_platform.h>
 17#include <asm/io.h>
 18
 19#define PPC4XX_TRNG_DEV_CTRL 0x60080
 20
 21#define PPC4XX_TRNGE 0x00020000
 22#define PPC4XX_TRNG_CTRL 0x0008
 23#define PPC4XX_TRNG_CTRL_DALM 0x20
 24#define PPC4XX_TRNG_STAT 0x0004
 25#define PPC4XX_TRNG_STAT_B 0x1
 26#define PPC4XX_TRNG_DATA 0x0000
 27
 28#define MODULE_NAME "ppc4xx_rng"
 29
 30static int ppc4xx_rng_data_present(struct hwrng *rng, int wait)
 31{
 32	void __iomem *rng_regs = (void __iomem *) rng->priv;
 33	int busy, i, present = 0;
 34
 35	for (i = 0; i < 20; i++) {
 36		busy = (in_le32(rng_regs + PPC4XX_TRNG_STAT) & PPC4XX_TRNG_STAT_B);
 37		if (!busy || !wait) {
 38			present = 1;
 39			break;
 40		}
 41		udelay(10);
 42	}
 43	return present;
 44}
 45
 46static int ppc4xx_rng_data_read(struct hwrng *rng, u32 *data)
 47{
 48	void __iomem *rng_regs = (void __iomem *) rng->priv;
 49	*data = in_le32(rng_regs + PPC4XX_TRNG_DATA);
 50	return 4;
 51}
 52
 53static int ppc4xx_rng_enable(int enable)
 54{
 55	struct device_node *ctrl;
 56	void __iomem *ctrl_reg;
 57	int err = 0;
 58	u32 val;
 59
 60	/* Find the main crypto device node and map it to turn the TRNG on */
 61	ctrl = of_find_compatible_node(NULL, NULL, "amcc,ppc4xx-crypto");
 62	if (!ctrl)
 63		return -ENODEV;
 64
 65	ctrl_reg = of_iomap(ctrl, 0);
 66	if (!ctrl_reg) {
 67		err = -ENODEV;
 68		goto out;
 69	}
 70
 71	val = in_le32(ctrl_reg + PPC4XX_TRNG_DEV_CTRL);
 72
 73	if (enable)
 74		val |= PPC4XX_TRNGE;
 75	else
 76		val = val & ~PPC4XX_TRNGE;
 77
 78	out_le32(ctrl_reg + PPC4XX_TRNG_DEV_CTRL, val);
 79	iounmap(ctrl_reg);
 80
 81out:
 82	of_node_put(ctrl);
 83
 84	return err;
 85}
 86
 87static struct hwrng ppc4xx_rng = {
 88	.name = MODULE_NAME,
 89	.data_present = ppc4xx_rng_data_present,
 90	.data_read = ppc4xx_rng_data_read,
 91};
 92
 93static int __devinit ppc4xx_rng_probe(struct platform_device *dev)
 94{
 95	void __iomem *rng_regs;
 96	int err = 0;
 97
 98	rng_regs = of_iomap(dev->dev.of_node, 0);
 99	if (!rng_regs)
100		return -ENODEV;
101
102	err = ppc4xx_rng_enable(1);
103	if (err)
104		return err;
105
106	out_le32(rng_regs + PPC4XX_TRNG_CTRL, PPC4XX_TRNG_CTRL_DALM);
107	ppc4xx_rng.priv = (unsigned long) rng_regs;
108
109	err = hwrng_register(&ppc4xx_rng);
110
111	return err;
112}
113
114static int __devexit ppc4xx_rng_remove(struct platform_device *dev)
115{
116	void __iomem *rng_regs = (void __iomem *) ppc4xx_rng.priv;
117
118	hwrng_unregister(&ppc4xx_rng);
119	ppc4xx_rng_enable(0);
120	iounmap(rng_regs);
121
122	return 0;
123}
124
125static struct of_device_id ppc4xx_rng_match[] = {
126	{ .compatible = "ppc4xx-rng", },
127	{ .compatible = "amcc,ppc460ex-rng", },
128	{ .compatible = "amcc,ppc440epx-rng", },
129	{},
130};
131
132static struct platform_driver ppc4xx_rng_driver = {
133	.driver = {
134		.name = MODULE_NAME,
135		.owner = THIS_MODULE,
136		.of_match_table = ppc4xx_rng_match,
137	},
138	.probe = ppc4xx_rng_probe,
139	.remove = ppc4xx_rng_remove,
140};
141
142static int __init ppc4xx_rng_init(void)
143{
144	return platform_driver_register(&ppc4xx_rng_driver);
145}
146module_init(ppc4xx_rng_init);
147
148static void __exit ppc4xx_rng_exit(void)
149{
150	platform_driver_unregister(&ppc4xx_rng_driver);
151}
152module_exit(ppc4xx_rng_exit);
153
154MODULE_LICENSE("GPL");
155MODULE_AUTHOR("Josh Boyer <jwboyer@linux.vnet.ibm.com>");
156MODULE_DESCRIPTION("HW RNG driver for PPC 4xx processors");