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// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Copyright 2013, Michael Ellerman, IBM Corporation.
*/
#define pr_fmt(fmt) "powernv-rng: " fmt
#include <linux/kernel.h>
#include <linux/of.h>
#include <linux/of_address.h>
#include <linux/of_platform.h>
#include <linux/slab.h>
#include <linux/smp.h>
#include <asm/archrandom.h>
#include <asm/cputable.h>
#include <asm/io.h>
#include <asm/prom.h>
#include <asm/machdep.h>
#include <asm/smp.h>
#include "powernv.h"
#define DARN_ERR 0xFFFFFFFFFFFFFFFFul
struct pnv_rng {
void __iomem *regs;
void __iomem *regs_real;
unsigned long mask;
};
static DEFINE_PER_CPU(struct pnv_rng *, pnv_rng);
static unsigned long rng_whiten(struct pnv_rng *rng, unsigned long val)
{
unsigned long parity;
/* Calculate the parity of the value */
asm (".machine push; \
.machine power7; \
popcntd %0,%1; \
.machine pop;"
: "=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;
}
static int pnv_get_random_darn(unsigned long *v)
{
unsigned long val;
/* Using DARN with L=1 - 64-bit conditioned random number */
asm volatile(PPC_DARN(%0, 1) : "=r"(val));
if (val == DARN_ERR)
return 0;
*v = val;
return 1;
}
static int __init initialise_darn(void)
{
unsigned long val;
int i;
if (!cpu_has_feature(CPU_FTR_ARCH_300))
return -ENODEV;
for (i = 0; i < 10; i++) {
if (pnv_get_random_darn(&val)) {
ppc_md.get_random_seed = pnv_get_random_darn;
return 0;
}
}
return -EIO;
}
int pnv_get_random_long(unsigned long *v)
{
struct pnv_rng *rng;
if (mfmsr() & MSR_DR) {
rng = get_cpu_var(pnv_rng);
*v = rng_whiten(rng, in_be64(rng->regs));
put_cpu_var(rng);
} else {
rng = raw_cpu_read(pnv_rng);
*v = rng_whiten(rng, __raw_rm_readq(rng->regs_real));
}
return 1;
}
EXPORT_SYMBOL_GPL(pnv_get_random_long);
static __init void rng_init_per_cpu(struct pnv_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 %pOF.\n", dn);
for_each_possible_cpu(cpu) {
if (per_cpu(pnv_rng, cpu) == NULL ||
cpu_to_chip_id(cpu) == chip_id) {
per_cpu(pnv_rng, cpu) = rng;
}
}
}
static __init int rng_create(struct device_node *dn)
{
struct pnv_rng *rng;
struct resource res;
unsigned long val;
rng = kzalloc(sizeof(*rng), GFP_KERNEL);
if (!rng)
return -ENOMEM;
if (of_address_to_resource(dn, 0, &res)) {
kfree(rng);
return -ENXIO;
}
rng->regs_real = (void __iomem *)res.start;
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);
ppc_md.get_random_seed = pnv_get_random_long;
return 0;
}
static int __init pnv_get_random_long_early(unsigned long *v)
{
struct device_node *dn;
if (!slab_is_available())
return 0;
if (cmpxchg(&ppc_md.get_random_seed, pnv_get_random_long_early,
NULL) != pnv_get_random_long_early)
return 0;
for_each_compatible_node(dn, NULL, "ibm,power-rng")
rng_create(dn);
if (!ppc_md.get_random_seed)
return 0;
return ppc_md.get_random_seed(v);
}
void __init pnv_rng_init(void)
{
struct device_node *dn;
/* Prefer darn over the rest. */
if (!initialise_darn())
return;
dn = of_find_compatible_node(NULL, NULL, "ibm,power-rng");
if (dn)
ppc_md.get_random_seed = pnv_get_random_long_early;
of_node_put(dn);
}
static int __init pnv_rng_late_init(void)
{
struct device_node *dn;
unsigned long v;
/* In case it wasn't called during init for some other reason. */
if (ppc_md.get_random_seed == pnv_get_random_long_early)
pnv_get_random_long_early(&v);
if (ppc_md.get_random_seed == pnv_get_random_long) {
for_each_compatible_node(dn, NULL, "ibm,power-rng")
of_platform_device_create(dn, NULL, NULL);
}
return 0;
}
machine_subsys_initcall(powernv, pnv_rng_late_init);
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