File content as of revision 189:f392fc9709a3:

/*
 *  Hardware entropy collector for the UNO_91H, using RDA's TRNG
 *
 *  Copyright (C) 2006-2018, ARM Limited, All Rights Reserved
 *  SPDX-License-Identifier: Apache-2.0
 *
 *  Licensed under the Apache License, Version 2.0 (the "License"); you may
 *  not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *  http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 */

#if DEVICE_TRNG

#include "cmsis.h"
#include "trng_api.h"
#include "us_ticker_api.h"

#define rRNG_CLKGATE        (RDA_SCU->CLKGATE0)
#define rRNG_CLKGEN         (RDA_DMACFG->dma_func_ctrl)
#define rTRNG_CTRL          (RDA_RNG->TCTRL)
#define rPRNG_DATA          (RDA_RNG->PD)

static uint32_t trng_inited = 0;

/** trng_get_byte
 *  @brief Get one byte of entropy from the RNG, assuming it is up and running.
 *  @param obj TRNG obj
 *  @param pointer to the hardware generated random byte.
 */
static void trng_get_byte(trng_t *obj, unsigned char *byte )
{
    if (0U == obj->byte_idx) {
        uint32_t start_time = us_ticker_read();
        /* Delay for PRNG data ready, generate 4-byte per 32us */
        while ((us_ticker_read() - start_time) <= 32);
    }
    *byte = (unsigned char)((rPRNG_DATA >> (obj->byte_idx << 3)) & 0x00FFUL);
    obj->byte_idx++;
    obj->byte_idx &= 0x03U;
}

void trng_init(trng_t *obj)
{
    uint32_t regval, start_time = 0;
    volatile uint32_t count = 10;

    if(trng_inited == 1)
        return;

    obj->dma_clk_flag = (uint8_t)((rRNG_CLKGATE >> 18) & 0x01U);
    obj->byte_idx = 0;
    if (0x00U == obj->dma_clk_flag) {
        /* DMA Peripheral clock enable */
        rRNG_CLKGATE |= (0x01UL << 18);
        /* dealy after clk en */
        while(count--);
    }
    /* RNG Engine clock enable */
    rRNG_CLKGEN |= (0x01UL << 30);
    /* Set TRNG enable bit, once mode */
    regval = rTRNG_CTRL |  ((0x01UL << 4) | (0xFFUL << 16));
    rTRNG_CTRL = regval & ~((0x01UL << 1) | (0x01UL << 2) | (0x01UL << 3));

    us_ticker_init();

    /*Entropy data was mixed by TRNG seed and noise, so we add one 32us delay to
      ensure all 32 bits of seed is entropy when init and 
      another delay to update noise data when get data. 
    */

     /* Delay for TRNG seed ready */
    start_time = us_ticker_read();
    while ((us_ticker_read() - start_time) <= 32);

    rTRNG_CTRL |= (0x01UL << 0);

    trng_inited = 1;
}

void trng_free(trng_t *obj)
{
    if(trng_inited == 0)
        return;
    /* Clear TRNG enable bit */
    rTRNG_CTRL = 0x00UL;
    /* RNG Engine clock disable */
    rRNG_CLKGEN &= ~(0x01UL << 30);
    if (0x00U == obj->dma_clk_flag) {
        /* DMA Peripheral clock disable */
        rRNG_CLKGATE &= ~(0x01UL << 18);
    }
    trng_inited = 0;
}

int trng_get_bytes(trng_t *obj, uint8_t *output, size_t length, size_t *output_length)
{
    int ret = 0;

    if(trng_inited != 1)
        return -1;

    /* Get Random byte */
    for (uint32_t i = 0; i < length; i++) {
        trng_get_byte(obj, output + i);
    }

    *output_length = length;

    return ret;
}

#endif