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_platform.h>
15 #include <linux/slab.h>
16 #include <asm/archrandom.h>
18 #include <asm/machdep.h>
26 static DEFINE_PER_CPU(struct powernv_rng *, powernv_rng);
29 static unsigned long rng_whiten(struct powernv_rng *rng, unsigned long val)
33 /* Calculate the parity of the value */
34 asm ("popcntd %0,%1" : "=r" (parity) : "r" (val));
36 /* xor our value with the previous mask */
39 /* update the mask based on the parity of this value */
40 rng->mask = (rng->mask << 1) | (parity & 1);
45 int powernv_get_random_long(unsigned long *v)
47 struct powernv_rng *rng;
49 rng = get_cpu_var(powernv_rng);
51 *v = rng_whiten(rng, in_be64(rng->regs));
57 EXPORT_SYMBOL_GPL(powernv_get_random_long);
59 static __init void rng_init_per_cpu(struct powernv_rng *rng,
60 struct device_node *dn)
64 chip_id = of_get_ibm_chip_id(dn);
66 pr_warn("No ibm,chip-id found for %s.\n", dn->full_name);
68 for_each_possible_cpu(cpu) {
69 if (per_cpu(powernv_rng, cpu) == NULL ||
70 cpu_to_chip_id(cpu) == chip_id) {
71 per_cpu(powernv_rng, cpu) = rng;
76 static __init int rng_create(struct device_node *dn)
78 struct powernv_rng *rng;
81 rng = kzalloc(sizeof(*rng), GFP_KERNEL);
85 rng->regs = of_iomap(dn, 0);
91 val = in_be64(rng->regs);
94 rng_init_per_cpu(rng, dn);
96 pr_info_once("Registering arch random hook.\n");
98 ppc_md.get_random_long = powernv_get_random_long;
103 static __init int rng_init(void)
105 struct device_node *dn;
108 for_each_compatible_node(dn, NULL, "ibm,power-rng") {
111 pr_err("Failed creating rng for %s (%d).\n",
116 /* Create devices for hwrng driver */
117 of_platform_device_create(dn, NULL, NULL);
122 subsys_initcall(rng_init);