drivers/char/hw_random/powernv-rng.c

   1 /*
   2  * Copyright 2013 Michael Ellerman, Guo Chao, IBM Corp.
   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)     KBUILD_MODNAME ": " fmt
  11
  12 #include <linux/module.h>
  13 #include <linux/mod_devicetable.h>
  14 #include <linux/kernel.h>
  15 #include <linux/platform_device.h>
  16 #include <linux/random.h>
  17 #include <linux/hw_random.h>
  18
  19 static int powernv_rng_read(struct hwrng *rng, void *data, size_t max, bool wait)
  20 {
  21         unsigned long *buf;
  22         int i, len;
  23
  24         /* We rely on rng_buffer_size() being >= sizeof(unsigned long) */
  25         len = max / sizeof(unsigned long);
  26
  27         buf = (unsigned long *)data;
  28
  29         for (i = 0; i < len; i++)
  30                 powernv_get_random_long(buf++);
  31
  32         return len * sizeof(unsigned long);
  33 }
  34
  35 static struct hwrng powernv_hwrng = {
  36         .name = "powernv-rng",
  37         .read = powernv_rng_read,
  38 };
  39
  40 static int powernv_rng_remove(struct platform_device *pdev)
  41 {
  42         hwrng_unregister(&powernv_hwrng);
  43
  44         return 0;
  45 }
  46
  47 static int powernv_rng_probe(struct platform_device *pdev)
  48 {
  49         int rc;
  50
  51         rc = hwrng_register(&powernv_hwrng);
  52         if (rc) {
  53                 /* We only register one device, ignore any others */
  54                 if (rc == -EEXIST)
  55                         rc = -ENODEV;
  56
  57                 return rc;
  58         }
  59
  60         pr_info("Registered powernv hwrng.\n");
  61
  62         return 0;
  63 }
  64
  65 static const struct of_device_id powernv_rng_match[] = {
  66         { .compatible   = "ibm,power-rng",},
  67         {},
  68 };
  69 MODULE_DEVICE_TABLE(of, powernv_rng_match);
  70
  71 static struct platform_driver powernv_rng_driver = {
  72         .driver = {
  73                 .name = "powernv_rng",
  74                 .of_match_table = powernv_rng_match,
  75         },
  76         .probe  = powernv_rng_probe,
  77         .remove = powernv_rng_remove,
  78 };
  79 module_platform_driver(powernv_rng_driver);
  80
  81 MODULE_LICENSE("GPL");
  82 MODULE_DESCRIPTION("Bare metal HWRNG driver for POWER7+ and above");