drivers/char/hw_random/pseries-rng.c

   1 /*
   2  * Copyright (C) 2010 Michael Neuling IBM Corporation
   3  *
   4  * Driver for the pseries hardware RNG for POWER7+ and above
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 as
   8  * published by the Free Software Foundation.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License
  16  * along with this program; if not, write to the Free Software
  17  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
  18  */
  19
  20 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  21
  22 #include <linux/kernel.h>
  23 #include <linux/module.h>
  24 #include <linux/hw_random.h>
  25 #include <asm/vio.h>
  26
  27
  28 static int pseries_rng_read(struct hwrng *rng, void *data, size_t max, bool wait)
  29 {
  30         u64 buffer[PLPAR_HCALL_BUFSIZE];
  31         int rc;
  32
  33         rc = plpar_hcall(H_RANDOM, (unsigned long *)buffer);
  34         if (rc != H_SUCCESS) {
  35                 pr_err_ratelimited("H_RANDOM call failed %d\n", rc);
  36                 return -EIO;
  37         }
  38         memcpy(data, buffer, 8);
  39
  40         /* The hypervisor interface returns 64 bits */
  41         return 8;
  42 }
  43
  44 /**
  45  * pseries_rng_get_desired_dma - Return desired DMA allocate for CMO operations
  46  *
  47  * This is a required function for a driver to operate in a CMO environment
  48  * but this device does not make use of DMA allocations, return 0.
  49  *
  50  * Return value:
  51  *      Number of bytes of IO data the driver will need to perform well -> 0
  52  */
  53 static unsigned long pseries_rng_get_desired_dma(struct vio_dev *vdev)
  54 {
  55         return 0;
  56 };
  57
  58 static struct hwrng pseries_rng = {
  59         .name           = KBUILD_MODNAME,
  60         .read           = pseries_rng_read,
  61 };
  62
  63 static int pseries_rng_probe(struct vio_dev *dev,
  64                 const struct vio_device_id *id)
  65 {
  66         return hwrng_register(&pseries_rng);
  67 }
  68
  69 static int pseries_rng_remove(struct vio_dev *dev)
  70 {
  71         hwrng_unregister(&pseries_rng);
  72         return 0;
  73 }
  74
  75 static const struct vio_device_id pseries_rng_driver_ids[] = {
  76         { "ibm,random-v1", "ibm,random"},
  77         { "", "" }
  78 };
  79 MODULE_DEVICE_TABLE(vio, pseries_rng_driver_ids);
  80
  81 static struct vio_driver pseries_rng_driver = {
  82         .name = KBUILD_MODNAME,
  83         .probe = pseries_rng_probe,
  84         .remove = pseries_rng_remove,
  85         .get_desired_dma = pseries_rng_get_desired_dma,
  86         .id_table = pseries_rng_driver_ids
  87 };
  88
  89 static int __init rng_init(void)
  90 {
  91         pr_info("Registering IBM pSeries RNG driver\n");
  92         return vio_register_driver(&pseries_rng_driver);
  93 }
  94
  95 module_init(rng_init);
  96
  97 static void __exit rng_exit(void)
  98 {
  99         vio_unregister_driver(&pseries_rng_driver);
 100 }
 101 module_exit(rng_exit);
 102
 103 MODULE_LICENSE("GPL");
 104 MODULE_AUTHOR("Michael Neuling <mikey@neuling.org>");
 105 MODULE_DESCRIPTION("H/W RNG driver for IBM pSeries processors");