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_read(struct hwrng *rng, void *data, size_t max, bool wait)
 29{
 30	u64 buffer[PLPAR_HCALL_BUFSIZE];
 31	size_t size = max < 8 ? max : 8;
 32	int rc;
 33
 34	rc = plpar_hcall(H_RANDOM, (unsigned long *)buffer);
 35	if (rc != H_SUCCESS) {
 36		pr_err_ratelimited("H_RANDOM call failed %d\n", rc);
 37		return -EIO;
 38	}
 39	memcpy(data, buffer, size);
 40
 41	/* The hypervisor interface returns 64 bits */
 42	return size;
 43}
 44
 45/**
 46 * pseries_rng_get_desired_dma - Return desired DMA allocate for CMO operations
 47 *
 48 * This is a required function for a driver to operate in a CMO environment
 49 * but this device does not make use of DMA allocations, return 0.
 50 *
 51 * Return value:
 52 *	Number of bytes of IO data the driver will need to perform well -> 0
 53 */
 54static unsigned long pseries_rng_get_desired_dma(struct vio_dev *vdev)
 55{
 56	return 0;
 57};
 58
 59static struct hwrng pseries_rng = {
 60	.name		= KBUILD_MODNAME,
 61	.read		= pseries_rng_read,
 62};
 63
 64static int pseries_rng_probe(struct vio_dev *dev,
 65		const struct vio_device_id *id)
 66{
 67	return hwrng_register(&pseries_rng);
 68}
 69
 70static int pseries_rng_remove(struct vio_dev *dev)
 71{
 72	hwrng_unregister(&pseries_rng);
 73	return 0;
 74}
 75
 76static struct vio_device_id pseries_rng_driver_ids[] = {
 77	{ "ibm,random-v1", "ibm,random"},
 78	{ "", "" }
 79};
 80MODULE_DEVICE_TABLE(vio, pseries_rng_driver_ids);
 81
 82static struct vio_driver pseries_rng_driver = {
 83	.name = KBUILD_MODNAME,
 84	.probe = pseries_rng_probe,
 85	.remove = pseries_rng_remove,
 86	.get_desired_dma = pseries_rng_get_desired_dma,
 87	.id_table = pseries_rng_driver_ids
 88};
 89
 90static int __init rng_init(void)
 91{
 92	pr_info("Registering IBM pSeries RNG driver\n");
 93	return vio_register_driver(&pseries_rng_driver);
 94}
 95
 96module_init(rng_init);
 97
 98static void __exit rng_exit(void)
 99{
100	vio_unregister_driver(&pseries_rng_driver);
101}
102module_exit(rng_exit);
103
104MODULE_LICENSE("GPL");
105MODULE_AUTHOR("Michael Neuling <mikey@neuling.org>");
106MODULE_DESCRIPTION("H/W RNG driver for IBM pSeries processors");