1a4da0d50SMichael Ellerman /* 2a4da0d50SMichael Ellerman * Copyright 2013, Michael Ellerman, IBM Corporation. 3a4da0d50SMichael Ellerman * 4a4da0d50SMichael Ellerman * This program is free software; you can redistribute it and/or 5a4da0d50SMichael Ellerman * modify it under the terms of the GNU General Public License 6a4da0d50SMichael Ellerman * as published by the Free Software Foundation; either version 7a4da0d50SMichael Ellerman * 2 of the License, or (at your option) any later version. 8a4da0d50SMichael Ellerman */ 9a4da0d50SMichael Ellerman 10a4da0d50SMichael Ellerman #define pr_fmt(fmt) "powernv-rng: " fmt 11a4da0d50SMichael Ellerman 12a4da0d50SMichael Ellerman #include <linux/kernel.h> 13a4da0d50SMichael Ellerman #include <linux/of.h> 141400b420SStephen Rothwell #include <linux/of_address.h> 15a4da0d50SMichael Ellerman #include <linux/of_platform.h> 16a4da0d50SMichael Ellerman #include <linux/slab.h> 171400b420SStephen Rothwell #include <linux/smp.h> 18a4da0d50SMichael Ellerman #include <asm/archrandom.h> 19a4da0d50SMichael Ellerman #include <asm/io.h> 201400b420SStephen Rothwell #include <asm/prom.h> 21a4da0d50SMichael Ellerman #include <asm/machdep.h> 223eb906c6SMichael Ellerman #include <asm/smp.h> 23a4da0d50SMichael Ellerman 24a4da0d50SMichael Ellerman 25a4da0d50SMichael Ellerman struct powernv_rng { 26a4da0d50SMichael Ellerman void __iomem *regs; 27a4da0d50SMichael Ellerman unsigned long mask; 28a4da0d50SMichael Ellerman }; 29a4da0d50SMichael Ellerman 30a4da0d50SMichael Ellerman static DEFINE_PER_CPU(struct powernv_rng *, powernv_rng); 31a4da0d50SMichael Ellerman 32a4da0d50SMichael Ellerman 33a4da0d50SMichael Ellerman static unsigned long rng_whiten(struct powernv_rng *rng, unsigned long val) 34a4da0d50SMichael Ellerman { 35a4da0d50SMichael Ellerman unsigned long parity; 36a4da0d50SMichael Ellerman 37a4da0d50SMichael Ellerman /* Calculate the parity of the value */ 38a4da0d50SMichael Ellerman asm ("popcntd %0,%1" : "=r" (parity) : "r" (val)); 39a4da0d50SMichael Ellerman 40a4da0d50SMichael Ellerman /* xor our value with the previous mask */ 41a4da0d50SMichael Ellerman val ^= rng->mask; 42a4da0d50SMichael Ellerman 43a4da0d50SMichael Ellerman /* update the mask based on the parity of this value */ 44a4da0d50SMichael Ellerman rng->mask = (rng->mask << 1) | (parity & 1); 45a4da0d50SMichael Ellerman 46a4da0d50SMichael Ellerman return val; 47a4da0d50SMichael Ellerman } 48a4da0d50SMichael Ellerman 49a4da0d50SMichael Ellerman int powernv_get_random_long(unsigned long *v) 50a4da0d50SMichael Ellerman { 51a4da0d50SMichael Ellerman struct powernv_rng *rng; 52a4da0d50SMichael Ellerman 53a4da0d50SMichael Ellerman rng = get_cpu_var(powernv_rng); 54a4da0d50SMichael Ellerman 55a4da0d50SMichael Ellerman *v = rng_whiten(rng, in_be64(rng->regs)); 56a4da0d50SMichael Ellerman 57a4da0d50SMichael Ellerman put_cpu_var(rng); 58a4da0d50SMichael Ellerman 59a4da0d50SMichael Ellerman return 1; 60a4da0d50SMichael Ellerman } 61a4da0d50SMichael Ellerman EXPORT_SYMBOL_GPL(powernv_get_random_long); 62a4da0d50SMichael Ellerman 63a4da0d50SMichael Ellerman static __init void rng_init_per_cpu(struct powernv_rng *rng, 64a4da0d50SMichael Ellerman struct device_node *dn) 65a4da0d50SMichael Ellerman { 66a4da0d50SMichael Ellerman int chip_id, cpu; 67a4da0d50SMichael Ellerman 68a4da0d50SMichael Ellerman chip_id = of_get_ibm_chip_id(dn); 69a4da0d50SMichael Ellerman if (chip_id == -1) 70a4da0d50SMichael Ellerman pr_warn("No ibm,chip-id found for %s.\n", dn->full_name); 71a4da0d50SMichael Ellerman 72a4da0d50SMichael Ellerman for_each_possible_cpu(cpu) { 73a4da0d50SMichael Ellerman if (per_cpu(powernv_rng, cpu) == NULL || 74a4da0d50SMichael Ellerman cpu_to_chip_id(cpu) == chip_id) { 75a4da0d50SMichael Ellerman per_cpu(powernv_rng, cpu) = rng; 76a4da0d50SMichael Ellerman } 77a4da0d50SMichael Ellerman } 78a4da0d50SMichael Ellerman } 79a4da0d50SMichael Ellerman 80a4da0d50SMichael Ellerman static __init int rng_create(struct device_node *dn) 81a4da0d50SMichael Ellerman { 82a4da0d50SMichael Ellerman struct powernv_rng *rng; 83a4da0d50SMichael Ellerman unsigned long val; 84a4da0d50SMichael Ellerman 85a4da0d50SMichael Ellerman rng = kzalloc(sizeof(*rng), GFP_KERNEL); 86a4da0d50SMichael Ellerman if (!rng) 87a4da0d50SMichael Ellerman return -ENOMEM; 88a4da0d50SMichael Ellerman 89a4da0d50SMichael Ellerman rng->regs = of_iomap(dn, 0); 90a4da0d50SMichael Ellerman if (!rng->regs) { 91a4da0d50SMichael Ellerman kfree(rng); 92a4da0d50SMichael Ellerman return -ENXIO; 93a4da0d50SMichael Ellerman } 94a4da0d50SMichael Ellerman 95a4da0d50SMichael Ellerman val = in_be64(rng->regs); 96a4da0d50SMichael Ellerman rng->mask = val; 97a4da0d50SMichael Ellerman 98a4da0d50SMichael Ellerman rng_init_per_cpu(rng, dn); 99a4da0d50SMichael Ellerman 100a4da0d50SMichael Ellerman pr_info_once("Registering arch random hook.\n"); 101a4da0d50SMichael Ellerman 102a4da0d50SMichael Ellerman ppc_md.get_random_long = powernv_get_random_long; 103a4da0d50SMichael Ellerman 104a4da0d50SMichael Ellerman return 0; 105a4da0d50SMichael Ellerman } 106a4da0d50SMichael Ellerman 107a4da0d50SMichael Ellerman static __init int rng_init(void) 108a4da0d50SMichael Ellerman { 109a4da0d50SMichael Ellerman struct device_node *dn; 110a4da0d50SMichael Ellerman int rc; 111a4da0d50SMichael Ellerman 112a4da0d50SMichael Ellerman for_each_compatible_node(dn, NULL, "ibm,power-rng") { 113a4da0d50SMichael Ellerman rc = rng_create(dn); 114a4da0d50SMichael Ellerman if (rc) { 115a4da0d50SMichael Ellerman pr_err("Failed creating rng for %s (%d).\n", 116a4da0d50SMichael Ellerman dn->full_name, rc); 117a4da0d50SMichael Ellerman continue; 118a4da0d50SMichael Ellerman } 119a4da0d50SMichael Ellerman 120a4da0d50SMichael Ellerman /* Create devices for hwrng driver */ 121a4da0d50SMichael Ellerman of_platform_device_create(dn, NULL, NULL); 122a4da0d50SMichael Ellerman } 123a4da0d50SMichael Ellerman 124a4da0d50SMichael Ellerman return 0; 125a4da0d50SMichael Ellerman } 126a4da0d50SMichael Ellerman subsys_initcall(rng_init); 127