blob: 8be2891f959067e16ca2be103e6f4ed2bdf0704a [file] [log] [blame]
/*
* 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);