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// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Derived from arch/powerpc/platforms/powernv/rng.c, which is:
* Copyright 2013, Michael Ellerman, IBM Corporation.
*/
#define pr_fmt(fmt) "microwatt-rng: " fmt
#include <linux/kernel.h>
#include <linux/smp.h>
#include <asm/archrandom.h>
#include <asm/cputable.h>
#include <asm/machdep.h>
#define DARN_ERR 0xFFFFFFFFFFFFFFFFul
static int microwatt_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 __init int rng_init(void)
{
unsigned long val;
int i;
for (i = 0; i < 10; i++) {
if (microwatt_get_random_darn(&val)) {
ppc_md.get_random_seed = microwatt_get_random_darn;
return 0;
}
}
pr_warn("Unable to use DARN for get_random_seed()\n");
return -EIO;
}
machine_subsys_initcall(, rng_init);
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