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/io.h>
  20 #include <asm/prom.h>
  21 #include <asm/machdep.h>
  22 #include <asm/smp.h>
  23
  24
  25 struct powernv_rng {
  26         void __iomem *regs;
  27         void __iomem *regs_real;
  28         unsigned long mask;
  29 };
  30
  31 static DEFINE_PER_CPU(struct powernv_rng *, powernv_rng);
  32
  33
  34 int powernv_hwrng_present(void)
  35 {
  36         struct powernv_rng *rng;
  37
  38         rng = get_cpu_var(powernv_rng);
  39         put_cpu_var(rng);
  40         return rng != NULL;
  41 }
  42
  43 static unsigned long rng_whiten(struct powernv_rng *rng, unsigned long val)
  44 {
  45         unsigned long parity;
  46
  47         /* Calculate the parity of the value */
  48         asm ("popcntd %0,%1" : "=r" (parity) : "r" (val));
  49
  50         /* xor our value with the previous mask */
  51         val ^= rng->mask;
  52
  53         /* update the mask based on the parity of this value */
  54         rng->mask = (rng->mask << 1) | (parity & 1);
  55
  56         return val;
  57 }
  58
  59 int powernv_get_random_real_mode(unsigned long *v)
  60 {
  61         struct powernv_rng *rng;
  62
  63         rng = raw_cpu_read(powernv_rng);
  64
  65         *v = rng_whiten(rng, in_rm64(rng->regs_real));
  66
  67         return 1;
  68 }
  69
  70 int powernv_get_random_long(unsigned long *v)
  71 {
  72         struct powernv_rng *rng;
  73
  74         rng = get_cpu_var(powernv_rng);
  75
  76         *v = rng_whiten(rng, in_be64(rng->regs));
  77
  78         put_cpu_var(rng);
  79
  80         return 1;
  81 }
  82 EXPORT_SYMBOL_GPL(powernv_get_random_long);
  83
  84 static __init void rng_init_per_cpu(struct powernv_rng *rng,
  85                                     struct device_node *dn)
  86 {
  87         int chip_id, cpu;
  88
  89         chip_id = of_get_ibm_chip_id(dn);
  90         if (chip_id == -1)
  91                 pr_warn("No ibm,chip-id found for %s.\n", dn->full_name);
  92
  93         for_each_possible_cpu(cpu) {
  94                 if (per_cpu(powernv_rng, cpu) == NULL ||
  95                     cpu_to_chip_id(cpu) == chip_id) {
  96                         per_cpu(powernv_rng, cpu) = rng;
  97                 }
  98         }
  99 }
 100
 101 static __init int rng_create(struct device_node *dn)
 102 {
 103         struct powernv_rng *rng;
 104         struct resource res;
 105         unsigned long val;
 106
 107         rng = kzalloc(sizeof(*rng), GFP_KERNEL);
 108         if (!rng)
 109                 return -ENOMEM;
 110
 111         if (of_address_to_resource(dn, 0, &res)) {
 112                 kfree(rng);
 113                 return -ENXIO;
 114         }
 115
 116         rng->regs_real = (void __iomem *)res.start;
 117
 118         rng->regs = of_iomap(dn, 0);
 119         if (!rng->regs) {
 120                 kfree(rng);
 121                 return -ENXIO;
 122         }
 123
 124         val = in_be64(rng->regs);
 125         rng->mask = val;
 126
 127         rng_init_per_cpu(rng, dn);
 128
 129         pr_info_once("Registering arch random hook.\n");
 130
 131         ppc_md.get_random_long = powernv_get_random_long;
 132
 133         return 0;
 134 }
 135
 136 static __init int rng_init(void)
 137 {
 138         struct device_node *dn;
 139         int rc;
 140
 141         for_each_compatible_node(dn, NULL, "ibm,power-rng") {
 142                 rc = rng_create(dn);
 143                 if (rc) {
 144                         pr_err("Failed creating rng for %s (%d).\n",
 145                                 dn->full_name, rc);
 146                         continue;
 147                 }
 148
 149                 /* Create devices for hwrng driver */
 150                 of_platform_device_create(dn, NULL, NULL);
 151         }
 152
 153         return 0;
 154 }
 155 machine_subsys_initcall(powernv, rng_init);