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);
191