arch/powerpc/platforms/powernv/rng.c

   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_address.h>
  15 #include <linux/of_platform.h>
  16 #include <linux/slab.h>
  17 #include <linux/smp.h>
  18 #include <asm/archrandom.h>
  19 #include <asm/cputable.h>
  20 #include <asm/io.h>
  21 #include <asm/prom.h>
  22 #include <asm/machdep.h>
  23 #include <asm/smp.h>
  24
  25 #define DARN_ERR 0xFFFFFFFFFFFFFFFFul
  26
  27 struct powernv_rng {
  28         void __iomem *regs;
  29         void __iomem *regs_real;
  30         unsigned long mask;
  31 };
  32
  33 static DEFINE_PER_CPU(struct powernv_rng *, powernv_rng);
  34
  35
  36 int powernv_hwrng_present(void)
  37 {
  38         struct powernv_rng *rng;
  39
  40         rng = get_cpu_var(powernv_rng);
  41         put_cpu_var(rng);
  42         return rng != NULL;
  43 }
  44
  45 static unsigned long rng_whiten(struct powernv_rng *rng, unsigned long val)
  46 {
  47         unsigned long parity;
  48
  49         /* Calculate the parity of the value */
  50         asm ("popcntd %0,%1" : "=r" (parity) : "r" (val));
  51
  52         /* xor our value with the previous mask */
  53         val ^= rng->mask;
  54
  55         /* update the mask based on the parity of this value */
  56         rng->mask = (rng->mask << 1) | (parity & 1);
  57
  58         return val;
  59 }
  60
  61 int powernv_get_random_real_mode(unsigned long *v)
  62 {
  63         struct powernv_rng *rng;
  64
  65         rng = raw_cpu_read(powernv_rng);
  66
  67         *v = rng_whiten(rng, __raw_rm_readq(rng->regs_real));
  68
  69         return 1;
  70 }
  71
  72 int powernv_get_random_darn(unsigned long *v)
  73 {
  74         unsigned long val;
  75
  76         /* Using DARN with L=1 - 64-bit conditioned random number */
  77         asm volatile(PPC_DARN(%0, 1) : "=r"(val));
  78
  79         if (val == DARN_ERR)
  80                 return 0;
  81
  82         *v = val;
  83
  84         return 1;
  85 }
  86
  87 static int initialise_darn(void)
  88 {
  89         unsigned long val;
  90         int i;
  91
  92         if (!cpu_has_feature(CPU_FTR_ARCH_300))
  93                 return -ENODEV;
  94
  95         for (i = 0; i < 10; i++) {
  96                 if (powernv_get_random_darn(&val)) {
  97                         ppc_md.get_random_seed = powernv_get_random_darn;
  98                         return 0;
  99                 }
 100         }
 101
 102         pr_warn("Unable to use DARN for get_random_seed()\n");
 103
 104         return -EIO;
 105 }
 106
 107 int powernv_get_random_long(unsigned long *v)
 108 {
 109         struct powernv_rng *rng;
 110
 111         rng = get_cpu_var(powernv_rng);
 112
 113         *v = rng_whiten(rng, in_be64(rng->regs));
 114
 115         put_cpu_var(rng);
 116
 117         return 1;
 118 }
 119 EXPORT_SYMBOL_GPL(powernv_get_random_long);
 120
 121 static __init void rng_init_per_cpu(struct powernv_rng *rng,
 122                                     struct device_node *dn)
 123 {
 124         int chip_id, cpu;
 125
 126         chip_id = of_get_ibm_chip_id(dn);
 127         if (chip_id == -1)
 128                 pr_warn("No ibm,chip-id found for %pOF.\n", dn);
 129
 130         for_each_possible_cpu(cpu) {
 131                 if (per_cpu(powernv_rng, cpu) == NULL ||
 132                     cpu_to_chip_id(cpu) == chip_id) {
 133                         per_cpu(powernv_rng, cpu) = rng;
 134                 }
 135         }
 136 }
 137
 138 static __init int rng_create(struct device_node *dn)
 139 {
 140         struct powernv_rng *rng;
 141         struct resource res;
 142         unsigned long val;
 143
 144         rng = kzalloc(sizeof(*rng), GFP_KERNEL);
 145         if (!rng)
 146                 return -ENOMEM;
 147
 148         if (of_address_to_resource(dn, 0, &res)) {
 149                 kfree(rng);
 150                 return -ENXIO;
 151         }
 152
 153         rng->regs_real = (void __iomem *)res.start;
 154
 155         rng->regs = of_iomap(dn, 0);
 156         if (!rng->regs) {
 157                 kfree(rng);
 158                 return -ENXIO;
 159         }
 160
 161         val = in_be64(rng->regs);
 162         rng->mask = val;
 163
 164         rng_init_per_cpu(rng, dn);
 165
 166         pr_info_once("Registering arch random hook.\n");
 167
 168         ppc_md.get_random_seed = powernv_get_random_long;
 169
 170         return 0;
 171 }
 172
 173 static __init int rng_init(void)
 174 {
 175         struct device_node *dn;
 176         int rc;
 177
 178         for_each_compatible_node(dn, NULL, "ibm,power-rng") {
 179                 rc = rng_create(dn);
 180                 if (rc) {
 181                         pr_err("Failed creating rng for %pOF (%d).\n",
 182                                 dn, rc);
 183                         continue;
 184                 }
 185
 186                 /* Create devices for hwrng driver */
 187                 of_platform_device_create(dn, NULL, NULL);
 188         }
 189
 190         initialise_darn();
 191
 192         return 0;
 193 }
 194 machine_subsys_initcall(powernv, rng_init);