1 /* 2 * Copyright 2013 Michael Ellerman, Guo Chao, IBM Corp. 3 * 4 * This program is free software; you can redistribute it and/or 5 * modify it under the terms of the GNU General Public License 6 * as published by the Free Software Foundation; either version 7 * 2 of the License, or (at your option) any later version. 8 */ 9 10 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 11 12 #include <linux/module.h> 13 #include <linux/mod_devicetable.h> 14 #include <linux/kernel.h> 15 #include <linux/platform_device.h> 16 #include <linux/random.h> 17 #include <linux/hw_random.h> 18 19 static int powernv_rng_read(struct hwrng *rng, void *data, size_t max, bool wait) 20 { 21 unsigned long *buf; 22 int i, len; 23 24 /* We rely on rng_buffer_size() being >= sizeof(unsigned long) */ 25 len = max / sizeof(unsigned long); 26 27 buf = (unsigned long *)data; 28 29 for (i = 0; i < len; i++) 30 powernv_get_random_long(buf++); 31 32 return len * sizeof(unsigned long); 33 } 34 35 static struct hwrng powernv_hwrng = { 36 .name = "powernv-rng", 37 .read = powernv_rng_read, 38 }; 39 40 static int powernv_rng_remove(struct platform_device *pdev) 41 { 42 hwrng_unregister(&powernv_hwrng); 43 44 return 0; 45 } 46 47 static int powernv_rng_probe(struct platform_device *pdev) 48 { 49 int rc; 50 51 rc = hwrng_register(&powernv_hwrng); 52 if (rc) { 53 /* We only register one device, ignore any others */ 54 if (rc == -EEXIST) 55 rc = -ENODEV; 56 57 return rc; 58 } 59 60 pr_info("Registered powernv hwrng.\n"); 61 62 return 0; 63 } 64 65 static const struct of_device_id powernv_rng_match[] = { 66 { .compatible = "ibm,power-rng",}, 67 {}, 68 }; 69 MODULE_DEVICE_TABLE(of, powernv_rng_match); 70 71 static struct platform_driver powernv_rng_driver = { 72 .driver = { 73 .name = "powernv_rng", 74 .of_match_table = powernv_rng_match, 75 }, 76 .probe = powernv_rng_probe, 77 .remove = powernv_rng_remove, 78 }; 79 module_platform_driver(powernv_rng_driver); 80 81 MODULE_LICENSE("GPL"); 82 MODULE_DESCRIPTION("Bare metal HWRNG driver for POWER7+ and above"); 83