1 // SPDX-License-Identifier: BSD-3-Clause 2 /* 3 * Copyright (c) 2018-2019, STMicroelectronics 4 */ 5 6 #include <assert.h> 7 #include <drivers/clk.h> 8 #include <drivers/clk_dt.h> 9 #include <drivers/stm32_rng.h> 10 #include <io.h> 11 #include <kernel/delay.h> 12 #include <kernel/dt.h> 13 #include <kernel/boot.h> 14 #include <kernel/panic.h> 15 #include <kernel/thread.h> 16 #include <libfdt.h> 17 #include <mm/core_memprot.h> 18 #include <stdbool.h> 19 #include <stm32_util.h> 20 #include <string.h> 21 22 #define DT_RNG_COMPAT "st,stm32-rng" 23 #define RNG_CR 0x00U 24 #define RNG_SR 0x04U 25 #define RNG_DR 0x08U 26 27 #define RNG_CR_RNGEN BIT(2) 28 #define RNG_CR_IE BIT(3) 29 #define RNG_CR_CED BIT(5) 30 31 #define RNG_SR_DRDY BIT(0) 32 #define RNG_SR_CECS BIT(1) 33 #define RNG_SR_SECS BIT(2) 34 #define RNG_SR_CEIS BIT(5) 35 #define RNG_SR_SEIS BIT(6) 36 37 #define RNG_TIMEOUT_US 10000 38 39 struct stm32_rng_instance { 40 struct io_pa_va base; 41 struct clk *clock; 42 unsigned int lock; 43 unsigned int refcount; 44 bool release_post_boot; 45 }; 46 47 static struct stm32_rng_instance *stm32_rng; 48 49 /* 50 * Extracts from the STM32 RNG specification: 51 * 52 * When a noise source (or seed) error occurs, the RNG stops generating 53 * random numbers and sets to “1” both SEIS and SECS bits to indicate 54 * that a seed error occurred. (...) 55 56 * The following sequence shall be used to fully recover from a seed 57 * error after the RNG initialization: 58 * 1. Clear the SEIS bit by writing it to “0”. 59 * 2. Read out 12 words from the RNG_DR register, and discard each of 60 * them in order to clean the pipeline. 61 * 3. Confirm that SEIS is still cleared. Random number generation is 62 * back to normal. 63 */ 64 static void conceal_seed_error(vaddr_t rng_base) 65 { 66 if (io_read32(rng_base + RNG_SR) & (RNG_SR_SECS | RNG_SR_SEIS)) { 67 size_t i = 0; 68 69 io_mask32(rng_base + RNG_SR, 0, RNG_SR_SEIS); 70 71 for (i = 12; i != 0; i--) 72 (void)io_read32(rng_base + RNG_DR); 73 74 if (io_read32(rng_base + RNG_SR) & RNG_SR_SEIS) 75 panic("RNG noise"); 76 } 77 } 78 79 #define RNG_FIFO_BYTE_DEPTH 16u 80 81 static TEE_Result stm32_rng_read_raw(vaddr_t rng_base, uint8_t *out, 82 size_t *size) 83 { 84 TEE_Result rc = TEE_ERROR_SECURITY; 85 uint64_t timeout_ref = timeout_init_us(RNG_TIMEOUT_US); 86 87 /* Wait RNG has produced well seeded random samples */ 88 while (!timeout_elapsed(timeout_ref)) { 89 conceal_seed_error(rng_base); 90 91 if (io_read32(rng_base + RNG_SR) & RNG_SR_DRDY) 92 break; 93 } 94 95 if (io_read32(rng_base + RNG_SR) & RNG_SR_DRDY) { 96 uint8_t *buf = out; 97 size_t req_size = MIN(RNG_FIFO_BYTE_DEPTH, *size); 98 size_t len = req_size; 99 100 /* RNG is ready: read up to 4 32bit words */ 101 while (len) { 102 uint32_t data32 = io_read32(rng_base + RNG_DR); 103 size_t sz = MIN(len, sizeof(uint32_t)); 104 105 memcpy(buf, &data32, sz); 106 buf += sz; 107 len -= sz; 108 } 109 rc = TEE_SUCCESS; 110 *size = req_size; 111 } 112 113 114 return rc; 115 } 116 117 static void gate_rng(bool enable, struct stm32_rng_instance *dev) 118 { 119 vaddr_t rng_cr = io_pa_or_va(&dev->base, 1) + RNG_CR; 120 uint32_t exceptions = may_spin_lock(&dev->lock); 121 122 if (enable) { 123 /* incr_refcnt return non zero if resource shall be enabled */ 124 if (incr_refcnt(&dev->refcount)) { 125 clk_enable(dev->clock); 126 io_write32(rng_cr, 0); 127 io_write32(rng_cr, RNG_CR_RNGEN | RNG_CR_CED); 128 } 129 } else { 130 /* decr_refcnt return non zero if resource shall be disabled */ 131 if (decr_refcnt(&dev->refcount)) { 132 io_write32(rng_cr, 0); 133 clk_disable(dev->clock); 134 } 135 } 136 137 may_spin_unlock(&dev->lock, exceptions); 138 } 139 140 TEE_Result stm32_rng_read(uint8_t *out, size_t size) 141 { 142 TEE_Result rc = 0; 143 uint32_t exceptions = 0; 144 vaddr_t rng_base = io_pa_or_va(&stm32_rng->base, 1); 145 uint8_t *out_ptr = out; 146 size_t out_size = 0; 147 148 if (!stm32_rng) { 149 DMSG("No RNG"); 150 return TEE_ERROR_NOT_SUPPORTED; 151 } 152 153 gate_rng(true, stm32_rng); 154 155 while (out_size < size) { 156 /* Read by chunks of the size the RNG FIFO depth */ 157 size_t sz = size - out_size; 158 159 exceptions = may_spin_lock(&stm32_rng->lock); 160 161 rc = stm32_rng_read_raw(rng_base, out_ptr, &sz); 162 163 may_spin_unlock(&stm32_rng->lock, exceptions); 164 165 if (rc) 166 goto bail; 167 168 out_size += sz; 169 out_ptr += sz; 170 } 171 172 bail: 173 gate_rng(false, stm32_rng); 174 if (rc) 175 memset(out, 0, size); 176 177 return rc; 178 } 179 180 #ifdef CFG_EMBED_DTB 181 static TEE_Result stm32_rng_init(void) 182 { 183 void *fdt = NULL; 184 int node = -1; 185 struct dt_node_info dt_info; 186 TEE_Result res = TEE_ERROR_GENERIC; 187 188 memset(&dt_info, 0, sizeof(dt_info)); 189 190 fdt = get_embedded_dt(); 191 if (!fdt) 192 panic(); 193 194 while (true) { 195 node = fdt_node_offset_by_compatible(fdt, node, DT_RNG_COMPAT); 196 if (node < 0) 197 break; 198 199 _fdt_fill_device_info(fdt, &dt_info, node); 200 201 if (!(dt_info.status & DT_STATUS_OK_SEC)) 202 continue; 203 204 if (stm32_rng) 205 panic(); 206 207 stm32_rng = calloc(1, sizeof(*stm32_rng)); 208 if (!stm32_rng) 209 panic(); 210 211 assert(dt_info.clock != DT_INFO_INVALID_CLOCK && 212 dt_info.reg != DT_INFO_INVALID_REG && 213 dt_info.reg_size != DT_INFO_INVALID_REG_SIZE); 214 215 if (dt_info.status & DT_STATUS_OK_NSEC) { 216 stm32mp_register_non_secure_periph_iomem(dt_info.reg); 217 stm32_rng->release_post_boot = true; 218 } else { 219 stm32mp_register_secure_periph_iomem(dt_info.reg); 220 } 221 222 stm32_rng->base.pa = dt_info.reg; 223 if (!io_pa_or_va_secure(&stm32_rng->base, dt_info.reg_size)) 224 panic(); 225 226 res = clk_dt_get_by_index(fdt, node, 0, &stm32_rng->clock); 227 if (res) 228 return res; 229 230 assert(stm32_rng->clock); 231 232 DMSG("RNG init"); 233 } 234 235 return TEE_SUCCESS; 236 } 237 238 early_init_late(stm32_rng_init); 239 240 static TEE_Result stm32_rng_release(void) 241 { 242 if (stm32_rng && stm32_rng->release_post_boot) { 243 DMSG("Release RNG driver"); 244 assert(!stm32_rng->refcount); 245 free(stm32_rng); 246 stm32_rng = NULL; 247 } 248 249 return TEE_SUCCESS; 250 } 251 252 release_init_resource(stm32_rng_release); 253 #endif /*CFG_EMBED_DTB*/ 254