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 pnv_rng {
25 void __iomem *regs;
26 void __iomem *regs_real;
27 unsigned long mask;
28 };
29
30 static DEFINE_PER_CPU(struct pnv_rng *, pnv_rng);
31
32 static unsigned long rng_whiten(struct pnv_rng *rng, unsigned long val)
33 {
34 unsigned long parity;
35
36 /* Calculate the parity of the value */
37 asm (".machine push; \
38 .machine power7; \
39 popcntd %0,%1; \
40 .machine pop;"
41 : "=r" (parity) : "r" (val));
42
43 /* xor our value with the previous mask */
44 val ^= rng->mask;
45
46 /* update the mask based on the parity of this value */
47 rng->mask = (rng->mask << 1) | (parity & 1);
48
49 return val;
50 }
51
52 static int pnv_get_random_darn(unsigned long *v)
53 {
54 unsigned long val;
55
56 /* Using DARN with L=1 - 64-bit conditioned random number */
57 asm volatile(PPC_DARN(%0, 1) : "=r"(val));
58
59 if (val == DARN_ERR)
60 return 0;
61
62 *v = val;
63
64 return 1;
65 }
66
67 static int __init initialise_darn(void)
68 {
69 unsigned long val;
70 int i;
71
72 if (!cpu_has_feature(CPU_FTR_ARCH_300))
73 return -ENODEV;
74
75 for (i = 0; i < 10; i++) {
76 if (pnv_get_random_darn(&val)) {
77 ppc_md.get_random_seed = pnv_get_random_darn;
78 return 0;
79 }
80 }
81 return -EIO;
82 }
83
84 int pnv_get_random_long(unsigned long *v)
85 {
86 struct pnv_rng *rng;
87
88 if (mfmsr() & MSR_DR) {
89 rng = get_cpu_var(pnv_rng);
90 *v = rng_whiten(rng, in_be64(rng->regs));
91 put_cpu_var(rng);
92 } else {
93 rng = raw_cpu_read(pnv_rng);
94 *v = rng_whiten(rng, __raw_rm_readq(rng->regs_real));
95 }
96 return 1;
97 }
98 EXPORT_SYMBOL_GPL(pnv_get_random_long);
99
100 static __init void rng_init_per_cpu(struct pnv_rng *rng,
101 struct device_node *dn)
102 {
103 int chip_id, cpu;
104
105 chip_id = of_get_ibm_chip_id(dn);
106 if (chip_id == -1)
107 pr_warn("No ibm,chip-id found for %pOF.\n", dn);
108
109 for_each_possible_cpu(cpu) {
110 if (per_cpu(pnv_rng, cpu) == NULL ||
111 cpu_to_chip_id(cpu) == chip_id) {
112 per_cpu(pnv_rng, cpu) = rng;
113 }
114 }
115 }
116
117 static __init int rng_create(struct device_node *dn)
118 {
119 struct pnv_rng *rng;
120 struct resource res;
121 unsigned long val;
122
123 rng = kzalloc(sizeof(*rng), GFP_KERNEL);
124 if (!rng)
125 return -ENOMEM;
126
127 if (of_address_to_resource(dn, 0, &res)) {
128 kfree(rng);
129 return -ENXIO;
130 }
131
132 rng->regs_real = (void __iomem *)res.start;
133
134 rng->regs = of_iomap(dn, 0);
135 if (!rng->regs) {
136 kfree(rng);
137 return -ENXIO;
138 }
139
140 val = in_be64(rng->regs);
141 rng->mask = val;
142
143 rng_init_per_cpu(rng, dn);
144
145 ppc_md.get_random_seed = pnv_get_random_long;
146
147 return 0;
148 }
149
150 static int __init pnv_get_random_long_early(unsigned long *v)
151 {
152 struct device_node *dn;
153
154 if (!slab_is_available())
155 return 0;
156
157 if (cmpxchg(&ppc_md.get_random_seed, pnv_get_random_long_early,
158 NULL) != pnv_get_random_long_early)
159 return 0;
160
161 for_each_compatible_node(dn, NULL, "ibm,power-rng")
162 rng_create(dn);
163
164 if (!ppc_md.get_random_seed)
165 return 0;
166 return ppc_md.get_random_seed(v);
167 }
168
169 void __init pnv_rng_init(void)
170 {
171 struct device_node *dn;
172
173 /* Prefer darn over the rest. */
174 if (!initialise_darn())
175 return;
176
177 dn = of_find_compatible_node(NULL, NULL, "ibm,power-rng");
178 if (dn)
179 ppc_md.get_random_seed = pnv_get_random_long_early;
180
181 of_node_put(dn);
182 }
183
184 static int __init pnv_rng_late_init(void)
185 {
186 struct device_node *dn;
187 unsigned long v;
188
189 /* In case it wasn't called during init for some other reason. */
190 if (ppc_md.get_random_seed == pnv_get_random_long_early)
191 pnv_get_random_long_early(&v);
192
193 if (ppc_md.get_random_seed == pnv_get_random_long) {
194 for_each_compatible_node(dn, NULL, "ibm,power-rng")
195 of_platform_device_create(dn, NULL, NULL);
196 }
197
198 return 0;
199 }
200 machine_subsys_initcall(powernv, pnv_rng_late_init);
201
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