1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * Copyright 2013, Michael Ellerman, IBM Corporation. 4 */ 5 6 #define pr_fmt(fmt) "powernv-rng: " fmt 7 8 #include <linux/kernel.h> 9 #include <linux/of.h> 10 #include <linux/of_address.h> 11 #include <linux/of_platform.h> 12 #include <linux/slab.h> 13 #include <linux/smp.h> 14 #include <asm/archrandom.h> 15 #include <asm/cputable.h> 16 #include <asm/io.h> 17 #include <asm/prom.h> 18 #include <asm/machdep.h> 19 #include <asm/smp.h> 20 21 #define DARN_ERR 0xFFFFFFFFFFFFFFFFul 22 23 struct powernv_rng { 24 void __iomem *regs; 25 void __iomem *regs_real; 26 unsigned long mask; 27 }; 28 29 static DEFINE_PER_CPU(struct powernv_rng *, powernv_rng); 30 31 32 int powernv_hwrng_present(void) 33 { 34 struct powernv_rng *rng; 35 36 rng = get_cpu_var(powernv_rng); 37 put_cpu_var(rng); 38 return rng != NULL; 39 } 40 41 static unsigned long rng_whiten(struct powernv_rng *rng, unsigned long val) 42 { 43 unsigned long parity; 44 45 /* Calculate the parity of the value */ 46 asm ("popcntd %0,%1" : "=r" (parity) : "r" (val)); 47 48 /* xor our value with the previous mask */ 49 val ^= rng->mask; 50 51 /* update the mask based on the parity of this value */ 52 rng->mask = (rng->mask << 1) | (parity & 1); 53 54 return val; 55 } 56 57 int powernv_get_random_real_mode(unsigned long *v) 58 { 59 struct powernv_rng *rng; 60 61 rng = raw_cpu_read(powernv_rng); 62 63 *v = rng_whiten(rng, __raw_rm_readq(rng->regs_real)); 64 65 return 1; 66 } 67 68 static int powernv_get_random_darn(unsigned long *v) 69 { 70 unsigned long val; 71 72 /* Using DARN with L=1 - 64-bit conditioned random number */ 73 asm volatile(PPC_DARN(%0, 1) : "=r"(val)); 74 75 if (val == DARN_ERR) 76 return 0; 77 78 *v = val; 79 80 return 1; 81 } 82 83 static int initialise_darn(void) 84 { 85 unsigned long val; 86 int i; 87 88 if (!cpu_has_feature(CPU_FTR_ARCH_300)) 89 return -ENODEV; 90 91 for (i = 0; i < 10; i++) { 92 if (powernv_get_random_darn(&val)) { 93 ppc_md.get_random_seed = powernv_get_random_darn; 94 return 0; 95 } 96 } 97 98 pr_warn("Unable to use DARN for get_random_seed()\n"); 99 100 return -EIO; 101 } 102 103 int powernv_get_random_long(unsigned long *v) 104 { 105 struct powernv_rng *rng; 106 107 rng = get_cpu_var(powernv_rng); 108 109 *v = rng_whiten(rng, in_be64(rng->regs)); 110 111 put_cpu_var(rng); 112 113 return 1; 114 } 115 EXPORT_SYMBOL_GPL(powernv_get_random_long); 116 117 static __init void rng_init_per_cpu(struct powernv_rng *rng, 118 struct device_node *dn) 119 { 120 int chip_id, cpu; 121 122 chip_id = of_get_ibm_chip_id(dn); 123 if (chip_id == -1) 124 pr_warn("No ibm,chip-id found for %pOF.\n", dn); 125 126 for_each_possible_cpu(cpu) { 127 if (per_cpu(powernv_rng, cpu) == NULL || 128 cpu_to_chip_id(cpu) == chip_id) { 129 per_cpu(powernv_rng, cpu) = rng; 130 } 131 } 132 } 133 134 static __init int rng_create(struct device_node *dn) 135 { 136 struct powernv_rng *rng; 137 struct resource res; 138 unsigned long val; 139 140 rng = kzalloc(sizeof(*rng), GFP_KERNEL); 141 if (!rng) 142 return -ENOMEM; 143 144 if (of_address_to_resource(dn, 0, &res)) { 145 kfree(rng); 146 return -ENXIO; 147 } 148 149 rng->regs_real = (void __iomem *)res.start; 150 151 rng->regs = of_iomap(dn, 0); 152 if (!rng->regs) { 153 kfree(rng); 154 return -ENXIO; 155 } 156 157 val = in_be64(rng->regs); 158 rng->mask = val; 159 160 rng_init_per_cpu(rng, dn); 161 162 pr_info_once("Registering arch random hook.\n"); 163 164 ppc_md.get_random_seed = powernv_get_random_long; 165 166 return 0; 167 } 168 169 static __init int rng_init(void) 170 { 171 struct device_node *dn; 172 int rc; 173 174 for_each_compatible_node(dn, NULL, "ibm,power-rng") { 175 rc = rng_create(dn); 176 if (rc) { 177 pr_err("Failed creating rng for %pOF (%d).\n", 178 dn, rc); 179 continue; 180 } 181 182 /* Create devices for hwrng driver */ 183 of_platform_device_create(dn, NULL, NULL); 184 } 185 186 initialise_darn(); 187 188 return 0; 189 } 190 machine_subsys_initcall(powernv, rng_init); 191