1// SPDX-License-Identifier: GPL-2.0 2/* 3 * Copyright (c) 2022, Linaro Limited 4 */ 5 6#define LOG_CATEGORY UCLASS_RNG 7 8#include <dm.h> 9#include <linker_lists.h> 10#include <log.h> 11#include <rng.h> 12#include <dm/device_compat.h> 13#include <linux/arm-smccc.h> 14#include <linux/bitops.h> 15#include <linux/kernel.h> 16#include <linux/psci.h> 17 18#define DRIVER_NAME "smccc-trng" 19 20/** 21 * Arm SMCCC TRNG firmware interface specification: 22 * https://developer.arm.com/documentation/den0098/latest/ 23 */ 24#define ARM_SMCCC_TRNG_VERSION 0x84000050 25#define ARM_SMCCC_TRNG_FEATURES 0x84000051 26#define ARM_SMCCC_TRNG_GET_UUID 0x84000052 27#define ARM_SMCCC_TRNG_RND_32 0x84000053 28#define ARM_SMCCC_TRNG_RND_64 0xC4000053 29 30#define ARM_SMCCC_RET_TRNG_SUCCESS ((ulong)0) 31#define ARM_SMCCC_RET_TRNG_NOT_SUPPORTED ((ulong)-1) 32#define ARM_SMCCC_RET_TRNG_INVALID_PARAMETER ((ulong)-2) 33#define ARM_SMCCC_RET_TRNG_NO_ENTROPY ((ulong)-3) 34 35#define TRNG_MAJOR_MASK GENMASK(30, 16) 36#define TRNG_MAJOR_SHIFT 16 37#define TRNG_MINOR_MASK GENMASK(15, 0) 38#define TRNG_MINOR_SHIFT 0 39 40#define TRNG_MAX_RND_64 (192 / 8) 41#define TRNG_MAX_RND_32 (96 / 8) 42 43/** 44 * struct smccc_trng_priv - Private data for SMCCC TRNG support 45 * 46 * @smc64 - True if TRNG_RND_64 is supported, false if TRNG_RND_32 is supported 47 */ 48struct smccc_trng_priv { 49 bool smc64; 50}; 51 52/* 53 * Copy random bytes from ulong SMCCC output register to target buffer 54 * Defines 2 function flavors for whether ARM_SMCCC_TRNG_RND_32 or 55 * ARM_SMCCC_TRNG_RND_64 was used to invoke the service. 56 */ 57static size_t smc32_copy_sample(u8 **ptr, size_t size, ulong *rnd) 58{ 59 size_t len = min(size, sizeof(u32)); 60 u32 sample = *rnd; 61 62 memcpy(*ptr, &sample, len); 63 *ptr += len; 64 65 return size - len; 66} 67 68static size_t smc64_copy_sample(u8 **ptr, size_t size, ulong *rnd) 69{ 70 size_t len = min(size, sizeof(u64)); 71 u64 sample = *rnd; 72 73 memcpy(*ptr, &sample, len); 74 *ptr += len; 75 76 return size - len; 77} 78 79static int smccc_trng_read(struct udevice *dev, void *data, size_t len) 80{ 81 struct psci_plat_data *smccc = dev_get_parent_plat(dev); 82 struct smccc_trng_priv *priv = dev_get_priv(dev); 83 struct arm_smccc_res res; 84 u32 func_id; 85 u8 *ptr = data; 86 size_t rem = len; 87 size_t max_sz; 88 size_t (*copy_sample)(u8 **ptr, size_t size, ulong *rnd); 89 90 if (priv->smc64) { 91 copy_sample = smc64_copy_sample; 92 func_id = ARM_SMCCC_TRNG_RND_64; 93 max_sz = TRNG_MAX_RND_64; 94 } else { 95 copy_sample = smc32_copy_sample; 96 func_id = ARM_SMCCC_TRNG_RND_32; 97 max_sz = TRNG_MAX_RND_32; 98 } 99 100 while (rem) { 101 size_t sz = min(rem, max_sz); 102 103 smccc->invoke_fn(func_id, sz * 8, 0, 0, 0, 0, 0, 0, &res); 104 105 switch (res.a0) { 106 case ARM_SMCCC_RET_TRNG_SUCCESS: 107 break; 108 case ARM_SMCCC_RET_TRNG_NO_ENTROPY: 109 continue; 110 default: 111 return -EIO; 112 } 113 114 rem -= sz; 115 116 sz = copy_sample(&ptr, sz, &res.a3); 117 if (sz) 118 sz = copy_sample(&ptr, sz, &res.a2); 119 if (sz) 120 sz = copy_sample(&ptr, sz, &res.a1); 121 } 122 123 return 0; 124} 125 126static const struct dm_rng_ops smccc_trng_ops = { 127 .read = smccc_trng_read, 128}; 129 130static bool smccc_trng_is_supported(void (*invoke_fn)(unsigned long a0, unsigned long a1, 131 unsigned long a2, unsigned long a3, 132 unsigned long a4, unsigned long a5, 133 unsigned long a6, unsigned long a7, 134 struct arm_smccc_res *res)) 135{ 136 struct arm_smccc_res res; 137 138 (*invoke_fn)(ARM_SMCCC_ARCH_FEATURES, ARM_SMCCC_TRNG_VERSION, 0, 0, 0, 0, 0, 0, &res); 139 if (res.a0 == ARM_SMCCC_RET_NOT_SUPPORTED) 140 return false; 141 142 (*invoke_fn)(ARM_SMCCC_TRNG_VERSION, 0, 0, 0, 0, 0, 0, 0, &res); 143 if (res.a0 & BIT(31)) 144 return false; 145 146 /* Test 64bit interface and fallback to 32bit interface */ 147 invoke_fn(ARM_SMCCC_TRNG_FEATURES, ARM_SMCCC_TRNG_RND_64, 148 0, 0, 0, 0, 0, 0, &res); 149 150 if (res.a0 == ARM_SMCCC_RET_TRNG_NOT_SUPPORTED) 151 invoke_fn(ARM_SMCCC_TRNG_FEATURES, ARM_SMCCC_TRNG_RND_32, 152 0, 0, 0, 0, 0, 0, &res); 153 154 return res.a0 == ARM_SMCCC_RET_TRNG_SUCCESS; 155} 156 157ARM_SMCCC_FEATURE_DRIVER(smccc_trng) = { 158 .driver_name = DRIVER_NAME, 159 .is_supported = smccc_trng_is_supported, 160}; 161 162static int smccc_trng_probe(struct udevice *dev) 163{ 164 struct psci_plat_data *smccc = dev_get_parent_plat(dev); 165 struct smccc_trng_priv *priv = dev_get_priv(dev); 166 struct arm_smccc_res res; 167 168 if (!smccc || !(smccc_trng_is_supported(smccc->invoke_fn))) 169 return -ENODEV; 170 171 /* At least one of 64bit and 32bit interfaces is available */ 172 smccc->invoke_fn(ARM_SMCCC_TRNG_FEATURES, ARM_SMCCC_TRNG_RND_64, 173 0, 0, 0, 0, 0, 0, &res); 174 priv->smc64 = (res.a0 == ARM_SMCCC_RET_TRNG_SUCCESS); 175 176#ifdef DEBUG 177 smccc->invoke_fn(ARM_SMCCC_TRNG_GET_UUID, 0, 0, 0, 0, 0, 0, 0, &res); 178 if (res.a0 != ARM_SMCCC_RET_TRNG_NOT_SUPPORTED) { 179 unsigned long uuid_a0 = res.a0; 180 unsigned long uuid_a1 = res.a1; 181 unsigned long uuid_a2 = res.a2; 182 unsigned long uuid_a3 = res.a3; 183 unsigned long major, minor; 184 185 smccc->invoke_fn(ARM_SMCCC_TRNG_VERSION, 0, 0, 0, 0, 0, 0, 0, &res); 186 major = (res.a0 & TRNG_MAJOR_MASK) >> TRNG_MAJOR_SHIFT; 187 minor = (res.a0 & TRNG_MINOR_MASK) >> TRNG_MINOR_SHIFT; 188 189 dev_dbg(dev, "Version %lu.%lu, UUID %08lx-%04lx-%04lx-%04lx-%04lx%08lx\n", 190 major, minor, uuid_a0, uuid_a1 >> 16, uuid_a1 & GENMASK(16, 0), 191 uuid_a2 >> 16, uuid_a2 & GENMASK(16, 0), uuid_a3); 192 } else { 193 dev_warn(dev, "Can't get TRNG UUID\n"); 194 } 195#endif 196 197 return 0; 198} 199 200U_BOOT_DRIVER(smccc_trng) = { 201 .name = DRIVER_NAME, 202 .id = UCLASS_RNG, 203 .ops = &smccc_trng_ops, 204 .probe = smccc_trng_probe, 205 .priv_auto = sizeof(struct smccc_trng_priv), 206}; 207