blob: a186f95a40225a762ec496bbda6378a6cfe21cbb [file] [log] [blame]
/*
* Copyright (c) 2016 ARM Limited.
*
* SPDX-License-Identifier: Apache-2.0
*/
#include <device.h>
#include <drivers/entropy.h>
#include <random/rand32.h>
#include <init.h>
#include "fsl_rnga.h"
static u8_t entropy_mcux_rnga_get_uint8(void)
{
u32_t random;
u8_t output = 0U;
int i;
RNGA_SetMode(RNG, kRNGA_ModeNormal);
/* The Reference manual states that back to back reads from
* the RNGA deliver one or two bits of entropy per 32-bit
* word, therefore to deliver 8 bits of entropy we need
* between 4 and 8 samples. Conservatively, we take 8.
*/
for (i = 0; i < 8; i++) {
status_t status;
status = RNGA_GetRandomData(RNG, &random, sizeof(random));
__ASSERT_NO_MSG(!status);
output ^= random;
}
RNGA_SetMode(RNG, kRNGA_ModeSleep);
return output;
}
static int entropy_mcux_rnga_get_entropy(struct device *dev, u8_t *buffer,
u16_t length)
{
int i;
ARG_UNUSED(dev);
for (i = 0; i < length; i++) {
buffer[i] = entropy_mcux_rnga_get_uint8();
}
return 0;
}
static const struct entropy_driver_api entropy_mcux_rnga_api_funcs = {
.get_entropy = entropy_mcux_rnga_get_entropy
};
static int entropy_mcux_rnga_init(struct device *);
DEVICE_AND_API_INIT(entropy_mcux_rnga, CONFIG_ENTROPY_NAME,
entropy_mcux_rnga_init, NULL, NULL,
PRE_KERNEL_1, CONFIG_KERNEL_INIT_PRIORITY_DEVICE,
&entropy_mcux_rnga_api_funcs);
static int entropy_mcux_rnga_init(struct device *dev)
{
u32_t seed = k_cycle_get_32();
ARG_UNUSED(dev);
RNGA_Init(RNG);
/* The range of seed values acquired by this method is likely
* to be relatively small. The RNGA hardware uses two free
* running oscillators to add entropy to the seed value, we
* take care below to ensure the read rate is lower than the
* rate at which the hardware can add entropy.
*/
RNGA_Seed(RNG, seed);
RNGA_SetMode(RNG, kRNGA_ModeSleep);
return 0;
}