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 15 #define DARN_ERR 0xFFFFFFFFFFFFFFFFul 16 17 static int microwatt_get_random_darn(unsigned long *v) 18 { 19 unsigned long val; 20 21 /* Using DARN with L=1 - 64-bit conditioned random number */ 22 asm volatile(PPC_DARN(%0, 1) : "=r"(val)); 23 24 if (val == DARN_ERR) 25 return 0; 26 27 *v = val; 28 29 return 1; 30 } 31 32 static __init int rng_init(void) 33 { 34 unsigned long val; 35 int i; 36 37 for (i = 0; i < 10; i++) { 38 if (microwatt_get_random_darn(&val)) { 39 ppc_md.get_random_seed = microwatt_get_random_darn; 40 return 0; 41 } 42 } 43 44 pr_warn("Unable to use DARN for get_random_seed()\n"); 45 46 return -EIO; 47 } 48 machine_subsys_initcall(, rng_init); 49