1 /*
2  * Copyright 2013, Michael Ellerman, IBM Corporation.
3  *
4  * This program is free software; you can redistribute it and/or
5  * modify it under the terms of the GNU General Public License
6  * as published by the Free Software Foundation; either version
7  * 2 of the License, or (at your option) any later version.
8  */
9 
10 #define pr_fmt(fmt)	"powernv-rng: " fmt
11 
12 #include <linux/kernel.h>
13 #include <linux/of.h>
14 #include <linux/of_address.h>
15 #include <linux/of_platform.h>
16 #include <linux/slab.h>
17 #include <linux/smp.h>
18 #include <asm/archrandom.h>
19 #include <asm/io.h>
20 #include <asm/prom.h>
21 #include <asm/machdep.h>
22 #include <asm/smp.h>
23 
24 
25 struct powernv_rng {
26 	void __iomem *regs;
27 	void __iomem *regs_real;
28 	unsigned long mask;
29 };
30 
31 static DEFINE_PER_CPU(struct powernv_rng *, powernv_rng);
32 
33 
34 int powernv_hwrng_present(void)
35 {
36 	struct powernv_rng *rng;
37 
38 	rng = get_cpu_var(powernv_rng);
39 	put_cpu_var(rng);
40 	return rng != NULL;
41 }
42 
43 static unsigned long rng_whiten(struct powernv_rng *rng, unsigned long val)
44 {
45 	unsigned long parity;
46 
47 	/* Calculate the parity of the value */
48 	asm ("popcntd %0,%1" : "=r" (parity) : "r" (val));
49 
50 	/* xor our value with the previous mask */
51 	val ^= rng->mask;
52 
53 	/* update the mask based on the parity of this value */
54 	rng->mask = (rng->mask << 1) | (parity & 1);
55 
56 	return val;
57 }
58 
59 int powernv_get_random_real_mode(unsigned long *v)
60 {
61 	struct powernv_rng *rng;
62 
63 	rng = raw_cpu_read(powernv_rng);
64 
65 	*v = rng_whiten(rng, in_rm64(rng->regs_real));
66 
67 	return 1;
68 }
69 
70 int powernv_get_random_long(unsigned long *v)
71 {
72 	struct powernv_rng *rng;
73 
74 	rng = get_cpu_var(powernv_rng);
75 
76 	*v = rng_whiten(rng, in_be64(rng->regs));
77 
78 	put_cpu_var(rng);
79 
80 	return 1;
81 }
82 EXPORT_SYMBOL_GPL(powernv_get_random_long);
83 
84 static __init void rng_init_per_cpu(struct powernv_rng *rng,
85 				    struct device_node *dn)
86 {
87 	int chip_id, cpu;
88 
89 	chip_id = of_get_ibm_chip_id(dn);
90 	if (chip_id == -1)
91 		pr_warn("No ibm,chip-id found for %s.\n", dn->full_name);
92 
93 	for_each_possible_cpu(cpu) {
94 		if (per_cpu(powernv_rng, cpu) == NULL ||
95 		    cpu_to_chip_id(cpu) == chip_id) {
96 			per_cpu(powernv_rng, cpu) = rng;
97 		}
98 	}
99 }
100 
101 static __init int rng_create(struct device_node *dn)
102 {
103 	struct powernv_rng *rng;
104 	struct resource res;
105 	unsigned long val;
106 
107 	rng = kzalloc(sizeof(*rng), GFP_KERNEL);
108 	if (!rng)
109 		return -ENOMEM;
110 
111 	if (of_address_to_resource(dn, 0, &res)) {
112 		kfree(rng);
113 		return -ENXIO;
114 	}
115 
116 	rng->regs_real = (void __iomem *)res.start;
117 
118 	rng->regs = of_iomap(dn, 0);
119 	if (!rng->regs) {
120 		kfree(rng);
121 		return -ENXIO;
122 	}
123 
124 	val = in_be64(rng->regs);
125 	rng->mask = val;
126 
127 	rng_init_per_cpu(rng, dn);
128 
129 	pr_info_once("Registering arch random hook.\n");
130 
131 	ppc_md.get_random_seed = powernv_get_random_long;
132 
133 	return 0;
134 }
135 
136 static __init int rng_init(void)
137 {
138 	struct device_node *dn;
139 	int rc;
140 
141 	for_each_compatible_node(dn, NULL, "ibm,power-rng") {
142 		rc = rng_create(dn);
143 		if (rc) {
144 			pr_err("Failed creating rng for %s (%d).\n",
145 				dn->full_name, rc);
146 			continue;
147 		}
148 
149 		/* Create devices for hwrng driver */
150 		of_platform_device_create(dn, NULL, NULL);
151 	}
152 
153 	return 0;
154 }
155 machine_subsys_initcall(powernv, rng_init);
156