| /* |
| * Copyright (c) 2017 Intel Corporation |
| * |
| * SPDX-License-Identifier: Apache-2.0 |
| */ |
| |
| #define DT_DRV_COMPAT espressif_esp32_trng |
| |
| #include <string.h> |
| #include <soc/rtc.h> |
| #include <soc/wdev_reg.h> |
| #include <soc/rtc_cntl_reg.h> |
| #include <soc/apb_ctrl_reg.h> |
| #include <esp_system.h> |
| #include <soc.h> |
| #include <esp_cpu.h> |
| #include <zephyr/drivers/entropy.h> |
| |
| static inline uint32_t entropy_esp32_get_u32(void) |
| { |
| /* The PRNG which implements WDEV_RANDOM register gets 2 bits |
| * of extra entropy from a hardware randomness source every APB clock cycle |
| * (provided WiFi or BT are enabled). To make sure entropy is not drained |
| * faster than it is added, this function needs to wait for at least 16 APB |
| * clock cycles after reading previous word. This implementation may actually |
| * wait a bit longer due to extra time spent in arithmetic and branch statements. |
| */ |
| |
| uint32_t cpu_to_apb_freq_ratio = |
| esp_clk_cpu_freq() / esp_clk_apb_freq(); |
| |
| static uint32_t last_ccount; |
| uint32_t ccount; |
| |
| do { |
| ccount = esp_cpu_get_cycle_count(); |
| } while (ccount - last_ccount < cpu_to_apb_freq_ratio * 16); |
| last_ccount = ccount; |
| |
| return REG_READ(WDEV_RND_REG); |
| } |
| |
| static int entropy_esp32_get_entropy(const struct device *dev, uint8_t *buf, |
| uint16_t len) |
| { |
| assert(buf != NULL); |
| uint8_t *buf_bytes = buf; |
| |
| while (len > 0) { |
| uint32_t word = entropy_esp32_get_u32(); |
| uint32_t to_copy = MIN(sizeof(word), len); |
| |
| memcpy(buf_bytes, &word, to_copy); |
| buf_bytes += to_copy; |
| len -= to_copy; |
| } |
| |
| return 0; |
| } |
| |
| static int entropy_esp32_init(const struct device *dev) |
| { |
| /* clock initialization handled by clock manager */ |
| return 0; |
| } |
| |
| static const struct entropy_driver_api entropy_esp32_api_funcs = { |
| .get_entropy = entropy_esp32_get_entropy |
| }; |
| |
| DEVICE_DT_INST_DEFINE(0, |
| entropy_esp32_init, NULL, NULL, NULL, |
| PRE_KERNEL_1, CONFIG_ENTROPY_INIT_PRIORITY, |
| &entropy_esp32_api_funcs); |