1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * Copyright 2013, Michael Ellerman, IBM Corporation.
4 */
5
6 #define pr_fmt(fmt) "powernv-rng: " fmt
7
8 #include <linux/kernel.h>
9 #include <linux/of.h>
10 #include <linux/of_address.h>
11 #include <linux/of_platform.h>
12 #include <linux/slab.h>
13 #include <linux/smp.h>
14 #include <asm/archrandom.h>
15 #include <asm/cputable.h>
16 #include <asm/io.h>
17 #include <asm/prom.h>
18 #include <asm/machdep.h>
19 #include <asm/smp.h>
20 #include "powernv.h"
21
22 #define DARN_ERR 0xFFFFFFFFFFFFFFFFul
23
24 struct powernv_rng {
25 void __iomem *regs;
26 void __iomem *regs_real;
27 unsigned long mask;
28 };
29
30 static DEFINE_PER_CPU(struct powernv_rng *, powernv_rng);
31
powernv_hwrng_present(void)32 int powernv_hwrng_present(void)
33 {
34 struct powernv_rng *rng;
35
36 rng = get_cpu_var(powernv_rng);
37 put_cpu_var(rng);
38 return rng != NULL;
39 }
40
rng_whiten(struct powernv_rng * rng,unsigned long val)41 static unsigned long rng_whiten(struct powernv_rng *rng, unsigned long val)
42 {
43 unsigned long parity;
44
45 /* Calculate the parity of the value */
46 asm (".machine push; \
47 .machine power7; \
48 popcntd %0,%1; \
49 .machine pop;"
50 : "=r" (parity) : "r" (val));
51
52 /* xor our value with the previous mask */
53 val ^= rng->mask;
54
55 /* update the mask based on the parity of this value */
56 rng->mask = (rng->mask << 1) | (parity & 1);
57
58 return val;
59 }
60
powernv_get_random_real_mode(unsigned long * v)61 int powernv_get_random_real_mode(unsigned long *v)
62 {
63 struct powernv_rng *rng;
64
65 rng = raw_cpu_read(powernv_rng);
66 if (!rng)
67 return 0;
68
69 *v = rng_whiten(rng, __raw_rm_readq(rng->regs_real));
70
71 return 1;
72 }
73
powernv_get_random_darn(unsigned long * v)74 static int powernv_get_random_darn(unsigned long *v)
75 {
76 unsigned long val;
77
78 /* Using DARN with L=1 - 64-bit conditioned random number */
79 asm volatile(PPC_DARN(%0, 1) : "=r"(val));
80
81 if (val == DARN_ERR)
82 return 0;
83
84 *v = val;
85
86 return 1;
87 }
88
initialise_darn(void)89 static int initialise_darn(void)
90 {
91 unsigned long val;
92 int i;
93
94 if (!cpu_has_feature(CPU_FTR_ARCH_300))
95 return -ENODEV;
96
97 for (i = 0; i < 10; i++) {
98 if (powernv_get_random_darn(&val)) {
99 ppc_md.get_random_seed = powernv_get_random_darn;
100 return 0;
101 }
102 }
103 return -EIO;
104 }
105
powernv_get_random_long(unsigned long * v)106 int powernv_get_random_long(unsigned long *v)
107 {
108 struct powernv_rng *rng;
109
110 rng = get_cpu_var(powernv_rng);
111
112 *v = rng_whiten(rng, in_be64(rng->regs));
113
114 put_cpu_var(rng);
115
116 return 1;
117 }
118 EXPORT_SYMBOL_GPL(powernv_get_random_long);
119
rng_init_per_cpu(struct powernv_rng * rng,struct device_node * dn)120 static __init void rng_init_per_cpu(struct powernv_rng *rng,
121 struct device_node *dn)
122 {
123 int chip_id, cpu;
124
125 chip_id = of_get_ibm_chip_id(dn);
126 if (chip_id == -1)
127 pr_warn("No ibm,chip-id found for %pOF.\n", dn);
128
129 for_each_possible_cpu(cpu) {
130 if (per_cpu(powernv_rng, cpu) == NULL ||
131 cpu_to_chip_id(cpu) == chip_id) {
132 per_cpu(powernv_rng, cpu) = rng;
133 }
134 }
135 }
136
rng_create(struct device_node * dn)137 static __init int rng_create(struct device_node *dn)
138 {
139 struct powernv_rng *rng;
140 struct resource res;
141 unsigned long val;
142
143 rng = kzalloc(sizeof(*rng), GFP_KERNEL);
144 if (!rng)
145 return -ENOMEM;
146
147 if (of_address_to_resource(dn, 0, &res)) {
148 kfree(rng);
149 return -ENXIO;
150 }
151
152 rng->regs_real = (void __iomem *)res.start;
153
154 rng->regs = of_iomap(dn, 0);
155 if (!rng->regs) {
156 kfree(rng);
157 return -ENXIO;
158 }
159
160 val = in_be64(rng->regs);
161 rng->mask = val;
162
163 rng_init_per_cpu(rng, dn);
164
165 ppc_md.get_random_seed = powernv_get_random_long;
166
167 return 0;
168 }
169
pnv_get_random_long_early(unsigned long * v)170 static int __init pnv_get_random_long_early(unsigned long *v)
171 {
172 struct device_node *dn;
173
174 if (!slab_is_available())
175 return 0;
176
177 if (cmpxchg(&ppc_md.get_random_seed, pnv_get_random_long_early,
178 NULL) != pnv_get_random_long_early)
179 return 0;
180
181 for_each_compatible_node(dn, NULL, "ibm,power-rng")
182 rng_create(dn);
183
184 if (!ppc_md.get_random_seed)
185 return 0;
186 return ppc_md.get_random_seed(v);
187 }
188
pnv_rng_init(void)189 void __init pnv_rng_init(void)
190 {
191 struct device_node *dn;
192
193 /* Prefer darn over the rest. */
194 if (!initialise_darn())
195 return;
196
197 dn = of_find_compatible_node(NULL, NULL, "ibm,power-rng");
198 if (dn)
199 ppc_md.get_random_seed = pnv_get_random_long_early;
200
201 of_node_put(dn);
202 }
203
pnv_rng_late_init(void)204 static int __init pnv_rng_late_init(void)
205 {
206 struct device_node *dn;
207 unsigned long v;
208
209 /* In case it wasn't called during init for some other reason. */
210 if (ppc_md.get_random_seed == pnv_get_random_long_early)
211 pnv_get_random_long_early(&v);
212
213 if (ppc_md.get_random_seed == powernv_get_random_long) {
214 for_each_compatible_node(dn, NULL, "ibm,power-rng")
215 of_platform_device_create(dn, NULL, NULL);
216 }
217
218 return 0;
219 }
220 machine_subsys_initcall(powernv, pnv_rng_late_init);
221