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
 28static int pseries_rng_data_read(struct hwrng *rng, u32 *data)
 29{
 30	int rc;
 31
 32	rc = plpar_hcall(H_RANDOM, (unsigned long *)data);
 33	if (rc != H_SUCCESS) {
 34		pr_err_ratelimited("H_RANDOM call failed %d\n", rc);
 35		return -EIO;
 36	}
 37
 38	/* The hypervisor interface returns 64 bits */
 39	return 8;
 40}
 41
 42/**
 43 * pseries_rng_get_desired_dma - Return desired DMA allocate for CMO operations
 44 *
 45 * This is a required function for a driver to operate in a CMO environment
 46 * but this device does not make use of DMA allocations, return 0.
 47 *
 48 * Return value:
 49 *	Number of bytes of IO data the driver will need to perform well -> 0
 50 */
 51static unsigned long pseries_rng_get_desired_dma(struct vio_dev *vdev)
 52{
 53	return 0;
 54};
 55
 56static struct hwrng pseries_rng = {
 57	.name		= KBUILD_MODNAME,
 58	.data_read	= pseries_rng_data_read,
 59};
 60
 61static int __init pseries_rng_probe(struct vio_dev *dev,
 62		const struct vio_device_id *id)
 63{
 64	return hwrng_register(&pseries_rng);
 65}
 66
 67static int __exit pseries_rng_remove(struct vio_dev *dev)
 68{
 69	hwrng_unregister(&pseries_rng);
 70	return 0;
 71}
 72
 73static struct vio_device_id pseries_rng_driver_ids[] = {
 74	{ "ibm,random-v1", "ibm,random"},
 75	{ "", "" }
 76};
 77MODULE_DEVICE_TABLE(vio, pseries_rng_driver_ids);
 78
 79static struct vio_driver pseries_rng_driver = {
 80	.name = KBUILD_MODNAME,
 81	.probe = pseries_rng_probe,
 82	.remove = pseries_rng_remove,
 83	.get_desired_dma = pseries_rng_get_desired_dma,
 84	.id_table = pseries_rng_driver_ids
 85};
 86
 87static int __init rng_init(void)
 88{
 89	printk(KERN_INFO "Registering IBM pSeries RNG driver\n");
 90	return vio_register_driver(&pseries_rng_driver);
 91}
 92
 93module_init(rng_init);
 94
 95static void __exit rng_exit(void)
 96{
 97	vio_unregister_driver(&pseries_rng_driver);
 98}
 99module_exit(rng_exit);
100
101MODULE_LICENSE("GPL");
102MODULE_AUTHOR("Michael Neuling <mikey@neuling.org>");
103MODULE_DESCRIPTION("H/W RNG driver for IBM pSeries processors");