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         unsigned long mask;
  28 };
  29
  30 static DEFINE_PER_CPU(struct powernv_rng *, powernv_rng);
  31
  32
  33 static unsigned long rng_whiten(struct powernv_rng *rng, unsigned long val)
  34 {
  35         unsigned long parity;
  36
  37         /* Calculate the parity of the value */
  38         asm ("popcntd %0,%1" : "=r" (parity) : "r" (val));
  39
  40         /* xor our value with the previous mask */
  41         val ^= rng->mask;
  42
  43         /* update the mask based on the parity of this value */
  44         rng->mask = (rng->mask << 1) | (parity & 1);
  45
  46         return val;
  47 }
  48
  49 int powernv_get_random_long(unsigned long *v)
  50 {
  51         struct powernv_rng *rng;
  52
  53         rng = get_cpu_var(powernv_rng);
  54
  55         *v = rng_whiten(rng, in_be64(rng->regs));
  56
  57         put_cpu_var(rng);
  58
  59         return 1;
  60 }
  61 EXPORT_SYMBOL_GPL(powernv_get_random_long);
  62
  63 static __init void rng_init_per_cpu(struct powernv_rng *rng,
  64                                     struct device_node *dn)
  65 {
  66         int chip_id, cpu;
  67
  68         chip_id = of_get_ibm_chip_id(dn);
  69         if (chip_id == -1)
  70                 pr_warn("No ibm,chip-id found for %s.\n", dn->full_name);
  71
  72         for_each_possible_cpu(cpu) {
  73                 if (per_cpu(powernv_rng, cpu) == NULL ||
  74                     cpu_to_chip_id(cpu) == chip_id) {
  75                         per_cpu(powernv_rng, cpu) = rng;
  76                 }
  77         }
  78 }
  79
  80 static __init int rng_create(struct device_node *dn)
  81 {
  82         struct powernv_rng *rng;
  83         unsigned long val;
  84
  85         rng = kzalloc(sizeof(*rng), GFP_KERNEL);
  86         if (!rng)
  87                 return -ENOMEM;
  88
  89         rng->regs = of_iomap(dn, 0);
  90         if (!rng->regs) {
  91                 kfree(rng);
  92                 return -ENXIO;
  93         }
  94
  95         val = in_be64(rng->regs);
  96         rng->mask = val;
  97
  98         rng_init_per_cpu(rng, dn);
  99
 100         pr_info_once("Registering arch random hook.\n");
 101
 102         ppc_md.get_random_long = powernv_get_random_long;
 103
 104         return 0;
 105 }
 106
 107 static __init int rng_init(void)
 108 {
 109         struct device_node *dn;
 110         int rc;
 111
 112         for_each_compatible_node(dn, NULL, "ibm,power-rng") {
 113                 rc = rng_create(dn);
 114                 if (rc) {
 115                         pr_err("Failed creating rng for %s (%d).\n",
 116                                 dn->full_name, rc);
 117                         continue;
 118                 }
 119
 120                 /* Create devices for hwrng driver */
 121                 of_platform_device_create(dn, NULL, NULL);
 122         }
 123
 124         return 0;
 125 }
 126 subsys_initcall(rng_init);