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 #include "powernv.h" 21 22 #define DARN_ERR 0xFFFFFFFFFFFFFFFFul 23 24 struct pnv_rng { 25 void __iomem *regs; 26 void __iomem *regs_real; 27 unsigned long mask; 28 }; 29 30 static DEFINE_PER_CPU(struct pnv_rng *, pnv_rng); 31 32 static unsigned long rng_whiten(struct pnv_rng *rng, unsigned long val) 33 { 34 unsigned long parity; 35 36 /* Calculate the parity of the value */ 37 asm (".machine push; \ 38 .machine power7; \ 39 popcntd %0,%1; \ 40 .machine pop;" 41 : "=r" (parity) : "r" (val)); 42 43 /* xor our value with the previous mask */ 44 val ^= rng->mask; 45 46 /* update the mask based on the parity of this value */ 47 rng->mask = (rng->mask << 1) | (parity & 1); 48 49 return val; 50 } 51 52 static int pnv_get_random_darn(unsigned long *v) 53 { 54 unsigned long val; 55 56 /* Using DARN with L=1 - 64-bit conditioned random number */ 57 asm volatile(PPC_DARN(%0, 1) : "=r"(val)); 58 59 if (val == DARN_ERR) 60 return 0; 61 62 *v = val; 63 64 return 1; 65 } 66 67 static int __init initialise_darn(void) 68 { 69 unsigned long val; 70 int i; 71 72 if (!cpu_has_feature(CPU_FTR_ARCH_300)) 73 return -ENODEV; 74 75 for (i = 0; i < 10; i++) { 76 if (pnv_get_random_darn(&val)) { 77 ppc_md.get_random_seed = pnv_get_random_darn; 78 return 0; 79 } 80 } 81 return -EIO; 82 } 83 84 int pnv_get_random_long(unsigned long *v) 85 { 86 struct pnv_rng *rng; 87 88 if (mfmsr() & MSR_DR) { 89 rng = get_cpu_var(pnv_rng); 90 *v = rng_whiten(rng, in_be64(rng->regs)); 91 put_cpu_var(rng); 92 } else { 93 rng = raw_cpu_read(pnv_rng); 94 *v = rng_whiten(rng, __raw_rm_readq(rng->regs_real)); 95 } 96 return 1; 97 } 98 EXPORT_SYMBOL_GPL(pnv_get_random_long); 99 100 static __init void rng_init_per_cpu(struct pnv_rng *rng, 101 struct device_node *dn) 102 { 103 int chip_id, cpu; 104 105 chip_id = of_get_ibm_chip_id(dn); 106 if (chip_id == -1) 107 pr_warn("No ibm,chip-id found for %pOF.\n", dn); 108 109 for_each_possible_cpu(cpu) { 110 if (per_cpu(pnv_rng, cpu) == NULL || 111 cpu_to_chip_id(cpu) == chip_id) { 112 per_cpu(pnv_rng, cpu) = rng; 113 } 114 } 115 } 116 117 static __init int rng_create(struct device_node *dn) 118 { 119 struct pnv_rng *rng; 120 struct resource res; 121 unsigned long val; 122 123 rng = kzalloc(sizeof(*rng), GFP_KERNEL); 124 if (!rng) 125 return -ENOMEM; 126 127 if (of_address_to_resource(dn, 0, &res)) { 128 kfree(rng); 129 return -ENXIO; 130 } 131 132 rng->regs_real = (void __iomem *)res.start; 133 134 rng->regs = of_iomap(dn, 0); 135 if (!rng->regs) { 136 kfree(rng); 137 return -ENXIO; 138 } 139 140 val = in_be64(rng->regs); 141 rng->mask = val; 142 143 rng_init_per_cpu(rng, dn); 144 145 ppc_md.get_random_seed = pnv_get_random_long; 146 147 return 0; 148 } 149 150 static int __init pnv_get_random_long_early(unsigned long *v) 151 { 152 struct device_node *dn; 153 154 if (!slab_is_available()) 155 return 0; 156 157 if (cmpxchg(&ppc_md.get_random_seed, pnv_get_random_long_early, 158 NULL) != pnv_get_random_long_early) 159 return 0; 160 161 for_each_compatible_node(dn, NULL, "ibm,power-rng") 162 rng_create(dn); 163 164 if (!ppc_md.get_random_seed) 165 return 0; 166 return ppc_md.get_random_seed(v); 167 } 168 169 void __init pnv_rng_init(void) 170 { 171 struct device_node *dn; 172 173 /* Prefer darn over the rest. */ 174 if (!initialise_darn()) 175 return; 176 177 dn = of_find_compatible_node(NULL, NULL, "ibm,power-rng"); 178 if (dn) 179 ppc_md.get_random_seed = pnv_get_random_long_early; 180 181 of_node_put(dn); 182 } 183 184 static int __init pnv_rng_late_init(void) 185 { 186 struct device_node *dn; 187 unsigned long v; 188 189 /* In case it wasn't called during init for some other reason. */ 190 if (ppc_md.get_random_seed == pnv_get_random_long_early) 191 pnv_get_random_long_early(&v); 192 193 if (ppc_md.get_random_seed == pnv_get_random_long) { 194 for_each_compatible_node(dn, NULL, "ibm,power-rng") 195 of_platform_device_create(dn, NULL, NULL); 196 } 197 198 return 0; 199 } 200 machine_subsys_initcall(powernv, pnv_rng_late_init); 201