char/hw_random/pseries-rng.c

0001 // SPDX-License-Identifier: GPL-2.0-only
0002 /*
0003  * Copyright (C) 2010 Michael Neuling IBM Corporation
0004  *
0005  * Driver for the pseries hardware RNG for POWER7+ and above
0006  */
0007
0008 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
0009
0010 #include <linux/kernel.h>
0011 #include <linux/module.h>
0012 #include <linux/hw_random.h>
0013 #include <asm/vio.h>
0014
0015
0016 static int pseries_rng_read(struct hwrng *rng, void *data, size_t max, bool wait)
0017 {
0018     u64 buffer[PLPAR_HCALL_BUFSIZE];
0019     int rc;
0020
0021     rc = plpar_hcall(H_RANDOM, (unsigned long *)buffer);
0022     if (rc != H_SUCCESS) {
0023         pr_err_ratelimited("H_RANDOM call failed %d\n", rc);
0024         return -EIO;
0025     }
0026     memcpy(data, buffer, 8);
0027
0028     /* The hypervisor interface returns 64 bits */
0029     return 8;
0030 }
0031
0032 /*
0033  * pseries_rng_get_desired_dma - Return desired DMA allocate for CMO operations
0034  *
0035  * This is a required function for a driver to operate in a CMO environment
0036  * but this device does not make use of DMA allocations, return 0.
0037  *
0038  * Return value:
0039  *  Number of bytes of IO data the driver will need to perform well -> 0
0040  */
0041 static unsigned long pseries_rng_get_desired_dma(struct vio_dev *vdev)
0042 {
0043     return 0;
0044 };
0045
0046 static struct hwrng pseries_rng = {
0047     .name       = KBUILD_MODNAME,
0048     .read       = pseries_rng_read,
0049 };
0050
0051 static int pseries_rng_probe(struct vio_dev *dev,
0052         const struct vio_device_id *id)
0053 {
0054     return hwrng_register(&pseries_rng);
0055 }
0056
0057 static void pseries_rng_remove(struct vio_dev *dev)
0058 {
0059     hwrng_unregister(&pseries_rng);
0060 }
0061
0062 static const struct vio_device_id pseries_rng_driver_ids[] = {
0063     { "ibm,random-v1", "ibm,random"},
0064     { "", "" }
0065 };
0066 MODULE_DEVICE_TABLE(vio, pseries_rng_driver_ids);
0067
0068 static struct vio_driver pseries_rng_driver = {
0069     .name = KBUILD_MODNAME,
0070     .probe = pseries_rng_probe,
0071     .remove = pseries_rng_remove,
0072     .get_desired_dma = pseries_rng_get_desired_dma,
0073     .id_table = pseries_rng_driver_ids
0074 };
0075
0076 static int __init rng_init(void)
0077 {
0078     pr_info("Registering IBM pSeries RNG driver\n");
0079     return vio_register_driver(&pseries_rng_driver);
0080 }
0081
0082 module_init(rng_init);
0083
0084 static void __exit rng_exit(void)
0085 {
0086     vio_unregister_driver(&pseries_rng_driver);
0087 }
0088 module_exit(rng_exit);
0089
0090 MODULE_LICENSE("GPL");
0091 MODULE_AUTHOR("Michael Neuling <mikey@neuling.org>");
0092 MODULE_DESCRIPTION("H/W RNG driver for IBM pSeries processors");