1/*
2 * Copyright 2013, Michael Ellerman, IBM Corporation.
3 *
4 * This program is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU General Public License
6 * as published by the Free Software Foundation; either version
7 * 2 of the License, or (at your option) any later version.
8 */
9
10#define pr_fmt(fmt)	"powernv-rng: " fmt
11
12#include <linux/kernel.h>
13#include <linux/of.h>
14#include <linux/of_address.h>
15#include <linux/of_platform.h>
16#include <linux/slab.h>
17#include <linux/smp.h>
18#include <asm/archrandom.h>
19#include <asm/io.h>
20#include <asm/prom.h>
21#include <asm/machdep.h>
22#include <asm/smp.h>
23
24
25struct powernv_rng {
26	void __iomem *regs;
27	void __iomem *regs_real;
28	unsigned long mask;
29};
30
31static DEFINE_PER_CPU(struct powernv_rng *, powernv_rng);
32
33
34int powernv_hwrng_present(void)
35{
36	struct powernv_rng *rng;
37
38	rng = get_cpu_var(powernv_rng);
39	put_cpu_var(rng);
40	return rng != NULL;
41}
42
43static unsigned long rng_whiten(struct powernv_rng *rng, unsigned long val)
44{
45	unsigned long parity;
46
47	/* Calculate the parity of the value */
48	asm ("popcntd %0,%1" : "=r" (parity) : "r" (val));
49
50	/* xor our value with the previous mask */
51	val ^= rng->mask;
52
53	/* update the mask based on the parity of this value */
54	rng->mask = (rng->mask << 1) | (parity & 1);
55
56	return val;
57}
58
59int powernv_get_random_real_mode(unsigned long *v)
60{
61	struct powernv_rng *rng;
62
63	rng = raw_cpu_read(powernv_rng);
64
65	*v = rng_whiten(rng, in_rm64(rng->regs_real));
66
67	return 1;
68}
69
70int powernv_get_random_long(unsigned long *v)
71{
72	struct powernv_rng *rng;
73
74	rng = get_cpu_var(powernv_rng);
75
76	*v = rng_whiten(rng, in_be64(rng->regs));
77
78	put_cpu_var(rng);
79
80	return 1;
81}
82EXPORT_SYMBOL_GPL(powernv_get_random_long);
83
84static __init void rng_init_per_cpu(struct powernv_rng *rng,
85				    struct device_node *dn)
86{
87	int chip_id, cpu;
88
89	chip_id = of_get_ibm_chip_id(dn);
90	if (chip_id == -1)
91		pr_warn("No ibm,chip-id found for %s.\n", dn->full_name);
92
93	for_each_possible_cpu(cpu) {
94		if (per_cpu(powernv_rng, cpu) == NULL ||
95		    cpu_to_chip_id(cpu) == chip_id) {
96			per_cpu(powernv_rng, cpu) = rng;
97		}
98	}
99}
100
101static __init int rng_create(struct device_node *dn)
102{
103	struct powernv_rng *rng;
104	struct resource res;
105	unsigned long val;
106
107	rng = kzalloc(sizeof(*rng), GFP_KERNEL);
108	if (!rng)
109		return -ENOMEM;
110
111	if (of_address_to_resource(dn, 0, &res)) {
112		kfree(rng);
113		return -ENXIO;
114	}
115
116	rng->regs_real = (void __iomem *)res.start;
117
118	rng->regs = of_iomap(dn, 0);
119	if (!rng->regs) {
120		kfree(rng);
121		return -ENXIO;
122	}
123
124	val = in_be64(rng->regs);
125	rng->mask = val;
126
127	rng_init_per_cpu(rng, dn);
128
129	pr_info_once("Registering arch random hook.\n");
130
131	ppc_md.get_random_seed = powernv_get_random_long;
132
133	return 0;
134}
135
136static __init int rng_init(void)
137{
138	struct device_node *dn;
139	int rc;
140
141	for_each_compatible_node(dn, NULL, "ibm,power-rng") {
142		rc = rng_create(dn);
143		if (rc) {
144			pr_err("Failed creating rng for %s (%d).\n",
145				dn->full_name, rc);
146			continue;
147		}
148
149		/* Create devices for hwrng driver */
150		of_platform_device_create(dn, NULL, NULL);
151	}
152
153	return 0;
154}
155machine_subsys_initcall(powernv, rng_init);
156