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