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
21 #define DARN_ERR 0xFFFFFFFFFFFFFFFFul
22
23 struct powernv_rng {
24 void __iomem *regs;
25 void __iomem *regs_real;
26 unsigned long mask;
27 };
28
29 static DEFINE_PER_CPU(struct powernv_rng *, powernv_rng);
30
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 ("popcntd %0,%1" : "=r" (parity) : "r" (val));
47
48 /* xor our value with the previous mask */
49 val ^= rng->mask;
50
51 /* update the mask based on the parity of this value */
52 rng->mask = (rng->mask << 1) | (parity & 1);
53
54 return val;
55 }
56
powernv_get_random_real_mode(unsigned long * v)57 int powernv_get_random_real_mode(unsigned long *v)
58 {
59 struct powernv_rng *rng;
60
61 rng = raw_cpu_read(powernv_rng);
62
63 *v = rng_whiten(rng, __raw_rm_readq(rng->regs_real));
64
65 return 1;
66 }
67
powernv_get_random_darn(unsigned long * v)68 static int powernv_get_random_darn(unsigned long *v)
69 {
70 unsigned long val;
71
72 /* Using DARN with L=1 - 64-bit conditioned random number */
73 asm volatile(PPC_DARN(%0, 1) : "=r"(val));
74
75 if (val == DARN_ERR)
76 return 0;
77
78 *v = val;
79
80 return 1;
81 }
82
initialise_darn(void)83 static int initialise_darn(void)
84 {
85 unsigned long val;
86 int i;
87
88 if (!cpu_has_feature(CPU_FTR_ARCH_300))
89 return -ENODEV;
90
91 for (i = 0; i < 10; i++) {
92 if (powernv_get_random_darn(&val)) {
93 ppc_md.get_random_seed = powernv_get_random_darn;
94 return 0;
95 }
96 }
97
98 pr_warn("Unable to use DARN for get_random_seed()\n");
99
100 return -EIO;
101 }
102
powernv_get_random_long(unsigned long * v)103 int powernv_get_random_long(unsigned long *v)
104 {
105 struct powernv_rng *rng;
106
107 rng = get_cpu_var(powernv_rng);
108
109 *v = rng_whiten(rng, in_be64(rng->regs));
110
111 put_cpu_var(rng);
112
113 return 1;
114 }
115 EXPORT_SYMBOL_GPL(powernv_get_random_long);
116
rng_init_per_cpu(struct powernv_rng * rng,struct device_node * dn)117 static __init void rng_init_per_cpu(struct powernv_rng *rng,
118 struct device_node *dn)
119 {
120 int chip_id, cpu;
121
122 chip_id = of_get_ibm_chip_id(dn);
123 if (chip_id == -1)
124 pr_warn("No ibm,chip-id found for %pOF.\n", dn);
125
126 for_each_possible_cpu(cpu) {
127 if (per_cpu(powernv_rng, cpu) == NULL ||
128 cpu_to_chip_id(cpu) == chip_id) {
129 per_cpu(powernv_rng, cpu) = rng;
130 }
131 }
132 }
133
rng_create(struct device_node * dn)134 static __init int rng_create(struct device_node *dn)
135 {
136 struct powernv_rng *rng;
137 struct resource res;
138 unsigned long val;
139
140 rng = kzalloc(sizeof(*rng), GFP_KERNEL);
141 if (!rng)
142 return -ENOMEM;
143
144 if (of_address_to_resource(dn, 0, &res)) {
145 kfree(rng);
146 return -ENXIO;
147 }
148
149 rng->regs_real = (void __iomem *)res.start;
150
151 rng->regs = of_iomap(dn, 0);
152 if (!rng->regs) {
153 kfree(rng);
154 return -ENXIO;
155 }
156
157 val = in_be64(rng->regs);
158 rng->mask = val;
159
160 rng_init_per_cpu(rng, dn);
161
162 pr_info_once("Registering arch random hook.\n");
163
164 ppc_md.get_random_seed = powernv_get_random_long;
165
166 return 0;
167 }
168
rng_init(void)169 static __init int rng_init(void)
170 {
171 struct device_node *dn;
172 int rc;
173
174 for_each_compatible_node(dn, NULL, "ibm,power-rng") {
175 rc = rng_create(dn);
176 if (rc) {
177 pr_err("Failed creating rng for %pOF (%d).\n",
178 dn, rc);
179 continue;
180 }
181
182 /* Create devices for hwrng driver */
183 of_platform_device_create(dn, NULL, NULL);
184 }
185
186 initialise_darn();
187
188 return 0;
189 }
190 machine_subsys_initcall(powernv, rng_init);
191