1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * Derived from arch/powerpc/platforms/powernv/rng.c, which is:
4 * Copyright 2013, Michael Ellerman, IBM Corporation.
5 */
6
7 #define pr_fmt(fmt) "microwatt-rng: " fmt
8
9 #include <linux/kernel.h>
10 #include <linux/smp.h>
11 #include <asm/archrandom.h>
12 #include <asm/cputable.h>
13 #include <asm/machdep.h>
14 #include "microwatt.h"
15
16 #define DARN_ERR 0xFFFFFFFFFFFFFFFFul
17
18 static int microwatt_get_random_darn(unsigned long *v)
19 {
20 unsigned long val;
21
22 /* Using DARN with L=1 - 64-bit conditioned random number */
23 asm volatile(PPC_DARN(%0, 1) : "=r"(val));
24
25 if (val == DARN_ERR)
26 return 0;
27
28 *v = val;
29
30 return 1;
31 }
32
33 void __init microwatt_rng_init(void)
34 {
35 unsigned long val;
36 int i;
37
38 for (i = 0; i < 10; i++) {
39 if (microwatt_get_random_darn(&val)) {
40 ppc_md.get_random_seed = microwatt_get_random_darn;
41 return;
42 }
43 }
44 }
45
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