| Michael Ellerman | a4da0d5 | 2013-10-11 14:07:57 +1100 | [diff] [blame^] | 1 | /* |
| 2 | * Copyright 2013, Michael Ellerman, IBM Corporation. |
| 3 | * |
| 4 | * This program is free software; you can redistribute it and/or |
| 5 | * modify it under the terms of the GNU General Public License |
| 6 | * as published by the Free Software Foundation; either version |
| 7 | * 2 of the License, or (at your option) any later version. |
| 8 | */ |
| 9 | |
| 10 | #define pr_fmt(fmt) "powernv-rng: " fmt |
| 11 | |
| 12 | #include <linux/kernel.h> |
| 13 | #include <linux/of.h> |
| 14 | #include <linux/of_platform.h> |
| 15 | #include <linux/slab.h> |
| 16 | #include <asm/archrandom.h> |
| 17 | #include <asm/io.h> |
| 18 | #include <asm/machdep.h> |
| 19 | |
| 20 | |
| 21 | struct powernv_rng { |
| 22 | void __iomem *regs; |
| 23 | unsigned long mask; |
| 24 | }; |
| 25 | |
| 26 | static DEFINE_PER_CPU(struct powernv_rng *, powernv_rng); |
| 27 | |
| 28 | |
| 29 | static unsigned long rng_whiten(struct powernv_rng *rng, unsigned long val) |
| 30 | { |
| 31 | unsigned long parity; |
| 32 | |
| 33 | /* Calculate the parity of the value */ |
| 34 | asm ("popcntd %0,%1" : "=r" (parity) : "r" (val)); |
| 35 | |
| 36 | /* xor our value with the previous mask */ |
| 37 | val ^= rng->mask; |
| 38 | |
| 39 | /* update the mask based on the parity of this value */ |
| 40 | rng->mask = (rng->mask << 1) | (parity & 1); |
| 41 | |
| 42 | return val; |
| 43 | } |
| 44 | |
| 45 | int powernv_get_random_long(unsigned long *v) |
| 46 | { |
| 47 | struct powernv_rng *rng; |
| 48 | |
| 49 | rng = get_cpu_var(powernv_rng); |
| 50 | |
| 51 | *v = rng_whiten(rng, in_be64(rng->regs)); |
| 52 | |
| 53 | put_cpu_var(rng); |
| 54 | |
| 55 | return 1; |
| 56 | } |
| 57 | EXPORT_SYMBOL_GPL(powernv_get_random_long); |
| 58 | |
| 59 | static __init void rng_init_per_cpu(struct powernv_rng *rng, |
| 60 | struct device_node *dn) |
| 61 | { |
| 62 | int chip_id, cpu; |
| 63 | |
| 64 | chip_id = of_get_ibm_chip_id(dn); |
| 65 | if (chip_id == -1) |
| 66 | pr_warn("No ibm,chip-id found for %s.\n", dn->full_name); |
| 67 | |
| 68 | for_each_possible_cpu(cpu) { |
| 69 | if (per_cpu(powernv_rng, cpu) == NULL || |
| 70 | cpu_to_chip_id(cpu) == chip_id) { |
| 71 | per_cpu(powernv_rng, cpu) = rng; |
| 72 | } |
| 73 | } |
| 74 | } |
| 75 | |
| 76 | static __init int rng_create(struct device_node *dn) |
| 77 | { |
| 78 | struct powernv_rng *rng; |
| 79 | unsigned long val; |
| 80 | |
| 81 | rng = kzalloc(sizeof(*rng), GFP_KERNEL); |
| 82 | if (!rng) |
| 83 | return -ENOMEM; |
| 84 | |
| 85 | rng->regs = of_iomap(dn, 0); |
| 86 | if (!rng->regs) { |
| 87 | kfree(rng); |
| 88 | return -ENXIO; |
| 89 | } |
| 90 | |
| 91 | val = in_be64(rng->regs); |
| 92 | rng->mask = val; |
| 93 | |
| 94 | rng_init_per_cpu(rng, dn); |
| 95 | |
| 96 | pr_info_once("Registering arch random hook.\n"); |
| 97 | |
| 98 | ppc_md.get_random_long = powernv_get_random_long; |
| 99 | |
| 100 | return 0; |
| 101 | } |
| 102 | |
| 103 | static __init int rng_init(void) |
| 104 | { |
| 105 | struct device_node *dn; |
| 106 | int rc; |
| 107 | |
| 108 | for_each_compatible_node(dn, NULL, "ibm,power-rng") { |
| 109 | rc = rng_create(dn); |
| 110 | if (rc) { |
| 111 | pr_err("Failed creating rng for %s (%d).\n", |
| 112 | dn->full_name, rc); |
| 113 | continue; |
| 114 | } |
| 115 | |
| 116 | /* Create devices for hwrng driver */ |
| 117 | of_platform_device_create(dn, NULL, NULL); |
| 118 | } |
| 119 | |
| 120 | return 0; |
| 121 | } |
| 122 | subsys_initcall(rng_init); |