Merge tag 'sched-urgent-2020-10-25' of git://git.kernel.org/pub/scm/linux/kernel...
[linux-2.6-microblaze.git] / arch / powerpc / platforms / powernv / rng.c
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
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
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
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
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
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
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
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
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
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);