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/*
* Copyright 2013, Michael Ellerman, IBM Corporation.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*/
#define pr_fmt(fmt) "powernv-rng: " fmt
#include <linux/kernel.h>
#include <linux/of.h>
#include <linux/of_platform.h>
#include <linux/slab.h>
#include <asm/archrandom.h>
#include <asm/io.h>
#include <asm/machdep.h>
struct powernv_rng {
void __iomem *regs;
unsigned long mask;
};
static DEFINE_PER_CPU(struct powernv_rng *, powernv_rng);
static unsigned long rng_whiten(struct powernv_rng *rng, unsigned long val)
{
unsigned long parity;
/* Calculate the parity of the value */
asm ("popcntd %0,%1" : "=r" (parity) : "r" (val));
/* xor our value with the previous mask */
val ^= rng->mask;
/* update the mask based on the parity of this value */
rng->mask = (rng->mask << 1) | (parity & 1);
return val;
}
int powernv_get_random_long(unsigned long *v)
{
struct powernv_rng *rng;
rng = get_cpu_var(powernv_rng);
*v = rng_whiten(rng, in_be64(rng->regs));
put_cpu_var(rng);
return 1;
}
EXPORT_SYMBOL_GPL(powernv_get_random_long);
static __init void rng_init_per_cpu(struct powernv_rng *rng,
struct device_node *dn)
{
int chip_id, cpu;
chip_id = of_get_ibm_chip_id(dn);
if (chip_id == -1)
pr_warn("No ibm,chip-id found for %s.\n", dn->full_name);
for_each_possible_cpu(cpu) {
if (per_cpu(powernv_rng, cpu) == NULL ||
cpu_to_chip_id(cpu) == chip_id) {
per_cpu(powernv_rng, cpu) = rng;
}
}
}
static __init int rng_create(struct device_node *dn)
{
struct powernv_rng *rng;
unsigned long val;
rng = kzalloc(sizeof(*rng), GFP_KERNEL);
if (!rng)
return -ENOMEM;
rng->regs = of_iomap(dn, 0);
if (!rng->regs) {
kfree(rng);
return -ENXIO;
}
val = in_be64(rng->regs);
rng->mask = val;
rng_init_per_cpu(rng, dn);
pr_info_once("Registering arch random hook.\n");
ppc_md.get_random_long = powernv_get_random_long;
return 0;
}
static __init int rng_init(void)
{
struct device_node *dn;
int rc;
for_each_compatible_node(dn, NULL, "ibm,power-rng") {
rc = rng_create(dn);
if (rc) {
pr_err("Failed creating rng for %s (%d).\n",
dn->full_name, rc);
continue;
}
/* Create devices for hwrng driver */
of_platform_device_create(dn, NULL, NULL);
}
return 0;
}
subsys_initcall(rng_init);
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