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
25 struct powernv_rng {
26 void __iomem *regs;
27 void __iomem *regs_real;
28 unsigned long mask;
29 };
30
31 static DEFINE_PER_CPU(struct powernv_rng *, powernv_rng);
32
33
powernv_hwrng_present(void)34 int 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
rng_whiten(struct powernv_rng * rng,unsigned long val)43 static 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
powernv_get_random_real_mode(unsigned long * v)59 int 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
powernv_get_random_long(unsigned long * v)70 int 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 }
82 EXPORT_SYMBOL_GPL(powernv_get_random_long);
83
rng_init_per_cpu(struct powernv_rng * rng,struct device_node * dn)84 static __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
rng_create(struct device_node * dn)101 static __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
rng_init(void)136 static __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 }
155 machine_subsys_initcall(powernv, rng_init);
156