drivers/char/hw_random/powernv-rng.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Copyright 2013 Michael Ellerman, Guo Chao, IBM Corp.
   4  */
   5
   6 #define pr_fmt(fmt)     KBUILD_MODNAME ": " fmt
   7
   8 #include <linux/module.h>
   9 #include <linux/mod_devicetable.h>
  10 #include <linux/kernel.h>
  11 #include <linux/platform_device.h>
  12 #include <linux/random.h>
  13 #include <linux/hw_random.h>
  14
  15 static int powernv_rng_read(struct hwrng *rng, void *data, size_t max, bool wait)
  16 {
  17         unsigned long *buf;
  18         int i, len;
  19
  20         /* We rely on rng_buffer_size() being >= sizeof(unsigned long) */
  21         len = max / sizeof(unsigned long);
  22
  23         buf = (unsigned long *)data;
  24
  25         for (i = 0; i < len; i++)
  26                 powernv_get_random_long(buf++);
  27
  28         return len * sizeof(unsigned long);
  29 }
  30
  31 static struct hwrng powernv_hwrng = {
  32         .name = "powernv-rng",
  33         .read = powernv_rng_read,
  34 };
  35
  36 static int powernv_rng_probe(struct platform_device *pdev)
  37 {
  38         int rc;
  39
  40         rc = devm_hwrng_register(&pdev->dev, &powernv_hwrng);
  41         if (rc) {
  42                 /* We only register one device, ignore any others */
  43                 if (rc == -EEXIST)
  44                         rc = -ENODEV;
  45
  46                 return rc;
  47         }
  48
  49         pr_info("Registered powernv hwrng.\n");
  50
  51         return 0;
  52 }
  53
  54 static const struct of_device_id powernv_rng_match[] = {
  55         { .compatible   = "ibm,power-rng",},
  56         {},
  57 };
  58 MODULE_DEVICE_TABLE(of, powernv_rng_match);
  59
  60 static struct platform_driver powernv_rng_driver = {
  61         .driver = {
  62                 .name = "powernv_rng",
  63                 .of_match_table = powernv_rng_match,
  64         },
  65         .probe  = powernv_rng_probe,
  66 };
  67 module_platform_driver(powernv_rng_driver);
  68
  69 MODULE_LICENSE("GPL");
  70 MODULE_DESCRIPTION("Bare metal HWRNG driver for POWER7+ and above");