drivers/char/hw_random/pseries-rng.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (C) 2010 Michael Neuling IBM Corporation
   4  *
   5  * Driver for the pseries hardware RNG for POWER7+ and above
   6  */
   7
   8 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
   9
  10 #include <linux/kernel.h>
  11 #include <linux/module.h>
  12 #include <linux/hw_random.h>
  13 #include <asm/vio.h>
  14
  15
  16 static int pseries_rng_read(struct hwrng *rng, void *data, size_t max, bool wait)
  17 {
  18         u64 buffer[PLPAR_HCALL_BUFSIZE];
  19         int rc;
  20
  21         rc = plpar_hcall(H_RANDOM, (unsigned long *)buffer);
  22         if (rc != H_SUCCESS) {
  23                 pr_err_ratelimited("H_RANDOM call failed %d\n", rc);
  24                 return -EIO;
  25         }
  26         memcpy(data, buffer, 8);
  27
  28         /* The hypervisor interface returns 64 bits */
  29         return 8;
  30 }
  31
  32 /**
  33  * pseries_rng_get_desired_dma - Return desired DMA allocate for CMO operations
  34  *
  35  * This is a required function for a driver to operate in a CMO environment
  36  * but this device does not make use of DMA allocations, return 0.
  37  *
  38  * Return value:
  39  *      Number of bytes of IO data the driver will need to perform well -> 0
  40  */
  41 static unsigned long pseries_rng_get_desired_dma(struct vio_dev *vdev)
  42 {
  43         return 0;
  44 };
  45
  46 static struct hwrng pseries_rng = {
  47         .name           = KBUILD_MODNAME,
  48         .read           = pseries_rng_read,
  49 };
  50
  51 static int pseries_rng_probe(struct vio_dev *dev,
  52                 const struct vio_device_id *id)
  53 {
  54         return hwrng_register(&pseries_rng);
  55 }
  56
  57 static int pseries_rng_remove(struct vio_dev *dev)
  58 {
  59         hwrng_unregister(&pseries_rng);
  60         return 0;
  61 }
  62
  63 static const struct vio_device_id pseries_rng_driver_ids[] = {
  64         { "ibm,random-v1", "ibm,random"},
  65         { "", "" }
  66 };
  67 MODULE_DEVICE_TABLE(vio, pseries_rng_driver_ids);
  68
  69 static struct vio_driver pseries_rng_driver = {
  70         .name = KBUILD_MODNAME,
  71         .probe = pseries_rng_probe,
  72         .remove = pseries_rng_remove,
  73         .get_desired_dma = pseries_rng_get_desired_dma,
  74         .id_table = pseries_rng_driver_ids
  75 };
  76
  77 static int __init rng_init(void)
  78 {
  79         pr_info("Registering IBM pSeries RNG driver\n");
  80         return vio_register_driver(&pseries_rng_driver);
  81 }
  82
  83 module_init(rng_init);
  84
  85 static void __exit rng_exit(void)
  86 {
  87         vio_unregister_driver(&pseries_rng_driver);
  88 }
  89 module_exit(rng_exit);
  90
  91 MODULE_LICENSE("GPL");
  92 MODULE_AUTHOR("Michael Neuling <mikey@neuling.org>");
  93 MODULE_DESCRIPTION("H/W RNG driver for IBM pSeries processors");