2 * Copyright 2013, Michael Ellerman, IBM Corporation.
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.
10 #define pr_fmt(fmt) "powernv-rng: " fmt
12 #include <linux/kernel.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>
21 #include <asm/machdep.h>
30 static DEFINE_PER_CPU(struct powernv_rng *, powernv_rng);
33 static unsigned long rng_whiten(struct powernv_rng *rng, unsigned long val)
37 /* Calculate the parity of the value */
38 asm ("popcntd %0,%1" : "=r" (parity) : "r" (val));
40 /* xor our value with the previous mask */
43 /* update the mask based on the parity of this value */
44 rng->mask = (rng->mask << 1) | (parity & 1);
49 int powernv_get_random_long(unsigned long *v)
51 struct powernv_rng *rng;
53 rng = get_cpu_var(powernv_rng);
55 *v = rng_whiten(rng, in_be64(rng->regs));
61 EXPORT_SYMBOL_GPL(powernv_get_random_long);
63 static __init void rng_init_per_cpu(struct powernv_rng *rng,
64 struct device_node *dn)
68 chip_id = of_get_ibm_chip_id(dn);
70 pr_warn("No ibm,chip-id found for %s.\n", dn->full_name);
72 for_each_possible_cpu(cpu) {
73 if (per_cpu(powernv_rng, cpu) == NULL ||
74 cpu_to_chip_id(cpu) == chip_id) {
75 per_cpu(powernv_rng, cpu) = rng;
80 static __init int rng_create(struct device_node *dn)
82 struct powernv_rng *rng;
85 rng = kzalloc(sizeof(*rng), GFP_KERNEL);
89 rng->regs = of_iomap(dn, 0);
95 val = in_be64(rng->regs);
98 rng_init_per_cpu(rng, dn);
100 pr_info_once("Registering arch random hook.\n");
102 ppc_md.get_random_long = powernv_get_random_long;
107 static __init int rng_init(void)
109 struct device_node *dn;
112 for_each_compatible_node(dn, NULL, "ibm,power-rng") {
115 pr_err("Failed creating rng for %s (%d).\n",
120 /* Create devices for hwrng driver */
121 of_platform_device_create(dn, NULL, NULL);
126 machine_subsys_initcall(powernv, rng_init);