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 TEE_Result stm32_rng_read_raw(vaddr_t rng_base, uint8_t *out, size_t *size) 82 { 83 bool enabled = false; 84 TEE_Result rc = TEE_ERROR_SECURITY; 85 uint64_t timeout_ref = timeout_init_us(RNG_TIMEOUT_US); 86 87 if (!(io_read32(rng_base + RNG_CR) & RNG_CR_RNGEN)) { 88 /* Enable RNG if not, clock error is disabled */ 89 io_write32(rng_base + RNG_CR, RNG_CR_RNGEN | RNG_CR_CED); 90 enabled = true; 91 } 92 93 /* Wait RNG has produced well seeded random samples */ 94 while (!timeout_elapsed(timeout_ref)) { 95 conceal_seed_error(rng_base); 96 97 if (io_read32(rng_base + RNG_SR) & RNG_SR_DRDY) 98 break; 99 } 100 101 if (io_read32(rng_base + RNG_SR) & RNG_SR_DRDY) { 102 uint8_t *buf = out; 103 size_t req_size = MIN(RNG_FIFO_BYTE_DEPTH, *size); 104 size_t len = req_size; 105 106 /* RNG is ready: read up to 4 32bit words */ 107 while (len) { 108 uint32_t data32 = io_read32(rng_base + RNG_DR); 109 size_t sz = MIN(len, sizeof(uint32_t)); 110 111 memcpy(buf, &data32, sz); 112 buf += sz; 113 len -= sz; 114 } 115 rc = TEE_SUCCESS; 116 *size = req_size; 117 } 118 119 if (enabled) 120 io_write32(rng_base + RNG_CR, 0); 121 122 return rc; 123 } 124 125 static void gate_rng(bool enable, struct stm32_rng_instance *dev) 126 { 127 vaddr_t rng_cr = io_pa_or_va(&dev->base, 1) + RNG_CR; 128 uint32_t exceptions = may_spin_lock(&dev->lock); 129 130 if (enable) { 131 /* incr_refcnt return non zero if resource shall be enabled */ 132 if (incr_refcnt(&dev->refcount)) { 133 clk_enable(dev->clock); 134 io_write32(rng_cr, 0); 135 io_write32(rng_cr, RNG_CR_RNGEN | RNG_CR_CED); 136 } 137 } else { 138 /* decr_refcnt return non zero if resource shall be disabled */ 139 if (decr_refcnt(&dev->refcount)) { 140 io_write32(rng_cr, 0); 141 clk_disable(dev->clock); 142 } 143 } 144 145 may_spin_unlock(&dev->lock, exceptions); 146 } 147 148 TEE_Result stm32_rng_read(uint8_t *out, size_t size) 149 { 150 TEE_Result rc = 0; 151 uint32_t exceptions = 0; 152 vaddr_t rng_base = io_pa_or_va(&stm32_rng->base, 1); 153 uint8_t *out_ptr = out; 154 size_t out_size = 0; 155 156 if (!stm32_rng) { 157 DMSG("No RNG"); 158 return TEE_ERROR_NOT_SUPPORTED; 159 } 160 161 gate_rng(true, stm32_rng); 162 163 while (out_size < size) { 164 /* Read by chunks of the size the RNG FIFO depth */ 165 size_t sz = size - out_size; 166 167 exceptions = may_spin_lock(&stm32_rng->lock); 168 169 rc = stm32_rng_read_raw(rng_base, out_ptr, &sz); 170 171 may_spin_unlock(&stm32_rng->lock, exceptions); 172 173 if (rc) 174 goto bail; 175 176 out_size += sz; 177 out_ptr += sz; 178 } 179 180 bail: 181 gate_rng(false, stm32_rng); 182 if (rc) 183 memset(out, 0, size); 184 185 return rc; 186 } 187 188 #ifdef CFG_EMBED_DTB 189 static TEE_Result stm32_rng_init(void) 190 { 191 void *fdt = NULL; 192 int node = -1; 193 struct dt_node_info dt_info; 194 TEE_Result res = TEE_ERROR_GENERIC; 195 196 memset(&dt_info, 0, sizeof(dt_info)); 197 198 fdt = get_embedded_dt(); 199 if (!fdt) 200 panic(); 201 202 while (true) { 203 node = fdt_node_offset_by_compatible(fdt, node, DT_RNG_COMPAT); 204 if (node < 0) 205 break; 206 207 _fdt_fill_device_info(fdt, &dt_info, node); 208 209 if (!(dt_info.status & DT_STATUS_OK_SEC)) 210 continue; 211 212 if (stm32_rng) 213 panic(); 214 215 stm32_rng = calloc(1, sizeof(*stm32_rng)); 216 if (!stm32_rng) 217 panic(); 218 219 assert(dt_info.clock != DT_INFO_INVALID_CLOCK && 220 dt_info.reg != DT_INFO_INVALID_REG && 221 dt_info.reg_size != DT_INFO_INVALID_REG_SIZE); 222 223 if (dt_info.status & DT_STATUS_OK_NSEC) { 224 stm32mp_register_non_secure_periph_iomem(dt_info.reg); 225 stm32_rng->release_post_boot = true; 226 } else { 227 stm32mp_register_secure_periph_iomem(dt_info.reg); 228 } 229 230 stm32_rng->base.pa = dt_info.reg; 231 if (!io_pa_or_va_secure(&stm32_rng->base, dt_info.reg_size)) 232 panic(); 233 234 res = clk_dt_get_by_index(fdt, node, 0, &stm32_rng->clock); 235 if (res) 236 return res; 237 238 assert(stm32_rng->clock); 239 240 DMSG("RNG init"); 241 } 242 243 return TEE_SUCCESS; 244 } 245 246 early_init_late(stm32_rng_init); 247 248 static TEE_Result stm32_rng_release(void) 249 { 250 if (stm32_rng && stm32_rng->release_post_boot) { 251 DMSG("Release RNG driver"); 252 assert(!stm32_rng->refcount); 253 free(stm32_rng); 254 stm32_rng = NULL; 255 } 256 257 return TEE_SUCCESS; 258 } 259 260 release_init_resource(stm32_rng_release); 261 #endif /*CFG_EMBED_DTB*/ 262