LXR linux/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
  25struct powernv_rng {
  26        void __iomem *regs;
  27        void __iomem *regs_real;
  28        unsigned long mask;
  29};
  30
  31static DEFINE_PER_CPU(struct powernv_rng *, powernv_rng);
  32
  33
  34int 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
  43static 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
  59int 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
  70int 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}
  82EXPORT_SYMBOL_GPL(powernv_get_random_long);
  83
  84static __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
 101static __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_seed = powernv_get_random_long;
 132
 133        return 0;
 134}
 135
 136static __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}
 155machine_subsys_initcall(powernv, rng_init);
 156