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