/**************************************************************************//**
 * @file     rng.c
 * @version  V3.01
 * @brief    Show how to get true random number.
 *
 * @copyright SPDX-License-Identifier: Apache-2.0
 * @copyright Copyright (C) 2020 Nuvoton Technology Corp. All rights reserved.
 *****************************************************************************/

#include <stdio.h>
#include "NuMicro.h"

/** @addtogroup Standard_Driver Standard Driver
  @{
*/

/** @addtogroup RNG_Driver RNG Driver
  @{
*/


/** @addtogroup RNG_EXPORTED_FUNCTIONS RNG Exported Functions
  @{
*/

typedef enum _RNG_KEY_SIZE
{
    KEY_128 = 0,
    KEY_192 = 2,
    KEY_224 = 3,
    KEY_233 = 4,
    KEY_255 = 5,
    KEY_256 = 6,
    KEY_283 = 7,
    KEY_384 = 8,
    KEY_409 = 9,
    KEY_512 = 10,
    KEY_521 = 11,
    KEY_571 = 12

} eRNG_SZ;


/**
 *  @brief      Basic Configuration of TRNG and PRNG
 *
 *  @details    The function is used to set the basic configuration for TRNG and PRNG.
 */
static void RNG_BasicConfig()
{
    int32_t i;
    int32_t timeout = 0x1000000;

    /* Enable TRNG & PRNG */
    CLK->AHBCLK0 |= CLK_AHBCLK0_CRPTCKEN_Msk;
    CLK->APBCLK1 |= CLK_APBCLK1_TRNGCKEN_Msk;

    /* Use LIRC as TRNG engine clock */
    CLK->PWRCTL |= CLK_PWRCTL_LIRCEN_Msk;
    while((CLK->STATUS & CLK_STATUS_LIRCSTB_Msk) == 0)
    {
        if(i++ > timeout) break; /* Wait LIRC time-out */
    }
    CLK->CLKSEL2 = (CLK->CLKSEL2 & (~CLK_CLKSEL2_TRNGSEL_Msk)) | CLK_CLKSEL2_TRNGSEL_LIRC;

}




/**
 *  @brief      Open random number generator
 *
 *  @return      0  Successful
 *              -1  Failed
 *
 *  @details    The function is used to disable rng interrupt.
 */
int32_t RNG_Open()
{
    int32_t i;
    int32_t timeout = 0x1000000;
    
    RNG_BasicConfig();
    
    /* TRNG Activate */
    TRNG->ACT |= TRNG_ACT_ACT_Msk;
    /* Waiting for ready */
    i = 0;
    while((TRNG->CTL & TRNG_CTL_READY_Msk) == 0)
    {
        if(i++ > timeout)
        {
            /* TRNG ready timeout */
            return -1;
        }
    }
    
    /* CLKPSC is default to 0. The performance maybe low but suitable for any cases */
    TRNG->CTL = 0; 
    
    /* Waiting for PRNG busy */
    i = 0;
    while((CRPT->PRNG_CTL & CRPT_PRNG_CTL_BUSY_Msk) == CRPT_PRNG_CTL_BUSY_Msk)
    {
        if(i++ > timeout)
        {
            /* PRNG busy timeout */
            return -1;
        }
    }

    /* Reload seed from TRNG only at first time */
    CRPT->PRNG_CTL = (PRNG_KEY_SIZE_256 << CRPT_PRNG_CTL_KEYSZ_Pos) | CRPT_PRNG_CTL_START_Msk | CRPT_PRNG_CTL_SEEDRLD_Msk | PRNG_CTL_SEEDSRC_TRNG;

    i = 0;
    while(CRPT->PRNG_CTL & CRPT_PRNG_CTL_BUSY_Msk)
    {
        if(i++ > timeout)
        {
            /* busy timeout */
            return -1;
        }
    }

    return 0;
}


/**
 *  @brief      Get random words
 *
 *  @param[in]  pu32Buf Buffer pointer to store the random number
 *
 *  @param[in]  nWords  Buffer size in word count. nWords must <= 8
 *
 *  @return     Word count of random number in buffer
 *
 *  @details    The function is used to generate random numbers
 */
int32_t RNG_Random(uint32_t *pu32Buf, int32_t nWords)
{
    int32_t i;
    int32_t timeout = 0x10000;

    /* Waiting for Busy */
    while(CRPT->PRNG_CTL & CRPT_PRNG_CTL_BUSY_Msk)
    {
        if(timeout-- < 0)
            return 0;
    }

    if(nWords > 8)
        nWords = 8;

    /* Trig to generate seed 256 bits random number */
    CRPT->PRNG_CTL = (6 << CRPT_PRNG_CTL_KEYSZ_Pos) | CRPT_PRNG_CTL_START_Msk;

    timeout = 0x10000;
    while(CRPT->PRNG_CTL & CRPT_PRNG_CTL_BUSY_Msk)
    {
        if(timeout-- < 0)
            return 0;
    }

    for(i = 0; i < nWords; i++)
    {
        pu32Buf[i] = CRPT->PRNG_KEY[i];
    }

    return nWords;
}



/**
 *  @brief      Initial function for ECDSA key generator for Key Store
 *
 *  @param[in]  u32KeySize  It could be PRNG_KEY_SIZE_128 ~ PRNG_KEY_SIZE_571
 *
 *  @param[in]  au32ECC_N   The N value of specified ECC curve.
 *
 *  @return     -1      Failed
 *              Others  The key number in KS SRAM
 *
 *  @details    The function is initial funciton of RNG_ECDSA function.
 *              This funciton should be called before calling RNG_ECDSA().
 */
int32_t RNG_ECDSA_Init(uint32_t u32KeySize, uint32_t au32ECC_N[18])
{
    int32_t i;
    
    /* Initial TRNG and PRNG for random number */
    if(RNG_Open())
        return -1;
  
    /* It is necessary to set ECC_N for ECDSA */
    for(i = 0; i < 18; i++)
        CRPT->ECC_N[i] = au32ECC_N[i];

    CRPT->PRNG_KSCTL = (KS_OWNER_ECC << CRPT_PRNG_KSCTL_OWNER_Pos) |
                       CRPT_PRNG_KSCTL_ECDSA_Msk |
                       (CRPT_PRNG_KSCTL_WDST_Msk) |
                       (KS_SRAM << CRPT_PRNG_KSCTL_WSDST_Pos);

    return 0;
}


/**
 *  @brief      To generate a key to KS SRAM for ECDSA.
 *
 *  @return     -1      Failed
 *              Others  The key number in KS SRAM
 *
 *  @details    The function is used to generate a key to KS SRAM for ECDSA.
 *              This key is necessary for ECDSA+Key Store function of ECC.
 */
int32_t RNG_ECDSA(uint32_t u32KeySize)
{

    int32_t timeout;
    int32_t i;

    /* Reload seed only at first time */
    CRPT->PRNG_CTL = (u32KeySize << CRPT_PRNG_CTL_KEYSZ_Pos) | CRPT_PRNG_CTL_START_Msk | PRNG_CTL_SEEDSRC_TRNG;

    timeout = 0x10000;
    i = 0;
    while(CRPT->PRNG_CTL & CRPT_PRNG_CTL_BUSY_Msk)
    {
        if(i++ > timeout)
        {
            return -1;
        }
    }

    if(CRPT->PRNG_KSSTS & CRPT_PRNG_KSSTS_KCTLERR_Msk)
    {
        return -1;
    }

    return (CRPT->PRNG_KSSTS & CRPT_PRNG_KSCTL_NUM_Msk);
}



/**
 *  @brief      Initial funciton for RNG_ECDH.
 *
 *  @param[in]  u32KeySize  It could be PRNG_KEY_SIZE_128 ~ PRNG_KEY_SIZE_571
 *
 *  @param[in]  au32ECC_N   The N value of specified ECC curve.
 *
 *  @return     -1      Failed
 *              Others  The key number in KS SRAM
 *
 *  @details    The function is initial function of RNG_ECDH.
 *              
 */
int32_t RNG_ECDH_Init(uint32_t u32KeySize, uint32_t au32ECC_N[18])
{
    int32_t i;
    
    /* Initial Random Number Generator */
    if(RNG_Open())
        return -1;
    
    /* It is necessary to set ECC_N for ECDSA */
    for(i = 0; i < 18; i++)
        CRPT->ECC_N[i] = au32ECC_N[i];

    CRPT->PRNG_KSCTL = (KS_OWNER_ECC << CRPT_PRNG_KSCTL_OWNER_Pos) |
                       (CRPT_PRNG_KSCTL_ECDH_Msk) |
                       (CRPT_PRNG_KSCTL_WDST_Msk) |
                       (KS_SRAM << CRPT_PRNG_KSCTL_WSDST_Pos);

    return 0;
}


/**
 *  @brief      To generate a key to KS SRAM for ECDH.
 *
 *  @return     -1      Failed
 *              Others  The key number in KS SRAM
 *
 *  @details    The function is used to generate a key to KS SRAM for ECDH.
 *              This key is necessary for ECDH+Key Store function of ECC.
 */
int32_t RNG_ECDH(uint32_t u32KeySize)
{
    int32_t timeout;
    int32_t i;

    /* Reload seed only at first time */
    CRPT->PRNG_CTL = (u32KeySize << CRPT_PRNG_CTL_KEYSZ_Pos) | CRPT_PRNG_CTL_START_Msk | PRNG_CTL_SEEDSRC_TRNG;

    timeout = 0x10000;
    i = 0;
    while(CRPT->PRNG_CTL & CRPT_PRNG_CTL_BUSY_Msk)
    {
        if(i++ > timeout)
            return -1;
    }

    if(CRPT->PRNG_KSSTS & CRPT_PRNG_KSSTS_KCTLERR_Msk)
        return -1;

    return (CRPT->PRNG_KSSTS & CRPT_PRNG_KSCTL_NUM_Msk);
}

/**@}*/ /* end of group RNG_EXPORTED_FUNCTIONS */

/**@}*/ /* end of group RNG_Driver */

/**@}*/ /* end of group Standard_Driver */