/*!
    \file    system_gd32f10x.c
    \brief   CMSIS Cortex-M3 Device Peripheral Access Layer Source File for
             GD32F10x Device Series
*/

/*
    Copyright (c) 2012 ARM LIMITED

    All rights reserved.

    Redistribution and use in source and binary forms, with or without modification, 
are permitted provided that the following conditions are met:

    1. Redistributions of source code must retain the above copyright notice, this 
       list of conditions and the following disclaimer.
    2. Redistributions in binary form must reproduce the above copyright notice, 
       this list of conditions and the following disclaimer in the documentation 
       and/or other materials provided with the distribution.
    3. Neither the name of the copyright holder nor the names of its contributors 
       may be used to endorse or promote products derived from this software without 
       specific prior written permission.

    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 
IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, 
INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 
NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR 
PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, 
WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 
ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY 
OF SUCH DAMAGE.
*/

/* This file refers the CMSIS standard, some adjustments are made according to GigaDevice chips */

#include "gd32f10x.h"

/* system frequency define */
#define __IRC8M           (IRC8M_VALUE)            /* internal 8 MHz RC oscillator frequency */
#define __HXTAL           (HXTAL_VALUE)            /* high speed crystal oscillator frequency */
#define __SYS_OSC_CLK     (__IRC8M)                /* main oscillator frequency */

#define VECT_TAB_OFFSET  (uint32_t)0x00            /* vector table base offset */

/* select a system clock by uncommenting the following line */
/* use IRC8M */
//#define __SYSTEM_CLOCK_48M_PLL_IRC8M            (uint32_t)(48000000)
//#define __SYSTEM_CLOCK_72M_PLL_IRC8M            (uint32_t)(72000000)
//#define __SYSTEM_CLOCK_108M_PLL_IRC8M           (uint32_t)(108000000)

/* use HXTAL (XD series CK_HXTAL = 8M, CL series CK_HXTAL = 25M) */
//#define __SYSTEM_CLOCK_HXTAL                    (uint32_t)(__HXTAL)
//#define __SYSTEM_CLOCK_24M_PLL_HXTAL            (uint32_t)(24000000)
//#define __SYSTEM_CLOCK_36M_PLL_HXTAL            (uint32_t)(36000000)
//#define __SYSTEM_CLOCK_48M_PLL_HXTAL            (uint32_t)(48000000)
//#define __SYSTEM_CLOCK_56M_PLL_HXTAL            (uint32_t)(56000000)
//#define __SYSTEM_CLOCK_72M_PLL_HXTAL            (uint32_t)(72000000)
//#define __SYSTEM_CLOCK_96M_PLL_HXTAL            (uint32_t)(96000000)
#define __SYSTEM_CLOCK_108M_PLL_HXTAL           (uint32_t)(108000000)

#define RCU_MODIFY(__delay)     do{                                     \
                                    volatile uint32_t i;                \
                                    if(0 != __delay){                   \
                                        RCU_CFG0 |= RCU_AHB_CKSYS_DIV2; \
                                        for(i=0; i<__delay; i++){       \
                                        }                               \
                                        RCU_CFG0 |= RCU_AHB_CKSYS_DIV4; \
                                        for(i=0; i<__delay; i++){       \
                                        }                               \
                                    }                                   \
                                }while(0)

#define SEL_IRC8M       0x00U
#define SEL_HXTAL       0x01U
#define SEL_PLL         0x02U

/* set the system clock frequency and declare the system clock configuration function */
#ifdef __SYSTEM_CLOCK_48M_PLL_IRC8M
uint32_t SystemCoreClock = __SYSTEM_CLOCK_48M_PLL_IRC8M;
static void system_clock_48m_irc8m(void);
#elif defined (__SYSTEM_CLOCK_72M_PLL_IRC8M)
uint32_t SystemCoreClock = __SYSTEM_CLOCK_72M_PLL_IRC8M;
static void system_clock_72m_irc8m(void);
#elif defined (__SYSTEM_CLOCK_108M_PLL_IRC8M)
uint32_t SystemCoreClock = __SYSTEM_CLOCK_108M_PLL_IRC8M;
static void system_clock_108m_irc8m(void);

#elif defined (__SYSTEM_CLOCK_HXTAL)
uint32_t SystemCoreClock = __SYSTEM_CLOCK_HXTAL;
static void system_clock_hxtal(void);
#elif defined (__SYSTEM_CLOCK_24M_PLL_HXTAL)
uint32_t SystemCoreClock = __SYSTEM_CLOCK_24M_PLL_HXTAL;
static void system_clock_24m_hxtal(void);
#elif defined (__SYSTEM_CLOCK_36M_PLL_HXTAL)
uint32_t SystemCoreClock = __SYSTEM_CLOCK_36M_PLL_HXTAL;
static void system_clock_36m_hxtal(void);
#elif defined (__SYSTEM_CLOCK_48M_PLL_HXTAL)
uint32_t SystemCoreClock = __SYSTEM_CLOCK_48M_PLL_HXTAL;
static void system_clock_48m_hxtal(void);
#elif defined (__SYSTEM_CLOCK_56M_PLL_HXTAL)
uint32_t SystemCoreClock = __SYSTEM_CLOCK_56M_PLL_HXTAL;
static void system_clock_56m_hxtal(void);
#elif defined (__SYSTEM_CLOCK_72M_PLL_HXTAL)
uint32_t SystemCoreClock = __SYSTEM_CLOCK_72M_PLL_HXTAL;
static void system_clock_72m_hxtal(void);
#elif defined (__SYSTEM_CLOCK_96M_PLL_HXTAL)
uint32_t SystemCoreClock = __SYSTEM_CLOCK_96M_PLL_HXTAL;
static void system_clock_96m_hxtal(void);
#elif defined (__SYSTEM_CLOCK_108M_PLL_HXTAL)
uint32_t SystemCoreClock = __SYSTEM_CLOCK_108M_PLL_HXTAL;
static void system_clock_108m_hxtal(void);
#endif /* __SYSTEM_CLOCK_48M_PLL_IRC8M */

/* configure the system clock */
static void system_clock_config(void);

/*!
    \brief      configure the system clock
    \param[in]  none
    \param[out] none
    \retval     none
*/
static void system_clock_config(void)
{
#ifdef __SYSTEM_CLOCK_HXTAL
    system_clock_hxtal();
#elif defined (__SYSTEM_CLOCK_24M_PLL_HXTAL)
    system_clock_24m_hxtal();
#elif defined (__SYSTEM_CLOCK_36M_PLL_HXTAL)
    system_clock_36m_hxtal();
#elif defined (__SYSTEM_CLOCK_48M_PLL_HXTAL)
    system_clock_48m_hxtal();
#elif defined (__SYSTEM_CLOCK_56M_PLL_HXTAL)
    system_clock_56m_hxtal();
#elif defined (__SYSTEM_CLOCK_72M_PLL_HXTAL)
    system_clock_72m_hxtal();
#elif defined (__SYSTEM_CLOCK_96M_PLL_HXTAL)
    system_clock_96m_hxtal();
#elif defined (__SYSTEM_CLOCK_108M_PLL_HXTAL)
    system_clock_108m_hxtal();

#elif defined (__SYSTEM_CLOCK_48M_PLL_IRC8M)
    system_clock_48m_irc8m();
#elif defined (__SYSTEM_CLOCK_72M_PLL_IRC8M)
    system_clock_72m_irc8m();
#elif defined (__SYSTEM_CLOCK_108M_PLL_IRC8M)
    system_clock_108m_irc8m();
#endif /* __SYSTEM_CLOCK_HXTAL */
}

/*!
    \brief      setup the microcontroller system, initialize the system
    \param[in]  none
    \param[out] none
    \retval     none
*/
void SystemInit(void)
{
    /* reset the RCC clock configuration to the default reset state */
    /* enable IRC8M */
    RCU_CTL |= RCU_CTL_IRC8MEN;
    while(0U == (RCU_CTL & RCU_CTL_IRC8MSTB)){
    }
    RCU_MODIFY(0x50);
    RCU_CFG0 &= ~RCU_CFG0_SCS;
    /* reset HXTALEN, CKMEN, PLLEN bits */
    RCU_CTL &= ~(RCU_CTL_HXTALEN | RCU_CTL_CKMEN | RCU_CTL_PLLEN);

    /* reset SCS, AHBPSC, APB1PSC, APB2PSC, ADCPSC, CKOUT0SEL bits */
    RCU_CFG0 &= ~(RCU_CFG0_SCS | RCU_CFG0_AHBPSC | RCU_CFG0_APB1PSC | RCU_CFG0_APB2PSC |
                  RCU_CFG0_ADCPSC | RCU_CFG0_ADCPSC_2 | RCU_CFG0_CKOUT0SEL);

    /* reset HXTALEN, CKMEN, PLLEN bits */
    RCU_CTL &= ~(RCU_CTL_HXTALEN | RCU_CTL_CKMEN | RCU_CTL_PLLEN);

    /* Reset HXTALBPS bit */
    RCU_CTL &= ~(RCU_CTL_HXTALBPS);

    /* reset PLLSEL, PREDV0_LSB, PLLMF, USBFSPSC bits */
    
#ifdef GD32F10X_CL
    RCU_CFG0 &= ~(RCU_CFG0_PLLSEL | RCU_CFG0_PREDV0_LSB | RCU_CFG0_PLLMF |
                  RCU_CFG0_USBFSPSC | RCU_CFG0_PLLMF_4);

    RCU_CFG1 = 0x00000000U;
#else
    RCU_CFG0 &= ~(RCU_CFG0_PLLSEL | RCU_CFG0_PREDV0 | RCU_CFG0_PLLMF |
                  RCU_CFG0_USBDPSC | RCU_CFG0_PLLMF_4);
#endif /* GD32F10X_CL */

#if (defined(GD32F10X_MD) || defined(GD32F10X_HD) || defined(GD32F10X_XD))
    /* reset HXTALEN, CKMEN and PLLEN bits */
    RCU_CTL &= ~(RCU_CTL_PLLEN | RCU_CTL_CKMEN | RCU_CTL_HXTALEN);
    /* disable all interrupts */
    RCU_INT = 0x009F0000U;
#elif defined(GD32F10X_CL)
    /* Reset HXTALEN, CKMEN, PLLEN, PLL1EN and PLL2EN bits */
    RCU_CTL &= ~(RCU_CTL_PLLEN | RCU_CTL_PLL1EN | RCU_CTL_PLL2EN | RCU_CTL_CKMEN | RCU_CTL_HXTALEN);
    /* disable all interrupts */
    RCU_INT = 0x00FF0000U;
#endif

    /* Configure the System clock source, PLL Multiplier, AHB/APBx prescalers and Flash settings */
    system_clock_config();
    
#ifdef VECT_TAB_SRAM
    nvic_vector_table_set(NVIC_VECTTAB_RAM, VECT_TAB_OFFSET);
#else
    nvic_vector_table_set(NVIC_VECTTAB_FLASH, VECT_TAB_OFFSET);
#endif
}

#ifdef __SYSTEM_CLOCK_HXTAL
/*!
    \brief      configure the system clock to HXTAL
    \param[in]  none
    \param[out] none
    \retval     none
*/
static void system_clock_hxtal(void)
{
    uint32_t timeout = 0U;
    uint32_t stab_flag = 0U;
    
    /* enable HXTAL */
    RCU_CTL |= RCU_CTL_HXTALEN;
    
    /* wait until HXTAL is stable or the startup time is longer than HXTAL_STARTUP_TIMEOUT */
    do{
        timeout++;
        stab_flag = (RCU_CTL & RCU_CTL_HXTALSTB);
    }while((0U == stab_flag) && (HXTAL_STARTUP_TIMEOUT != timeout));
    
    /* if fail */
    if(0U == (RCU_CTL & RCU_CTL_HXTALSTB)){
        while(1){
        }
    }
    
    /* AHB = SYSCLK */
    RCU_CFG0 |= RCU_AHB_CKSYS_DIV1;
    /* APB2 = AHB/1 */
    RCU_CFG0 |= RCU_APB2_CKAHB_DIV1;
    /* APB1 = AHB/2 */
    RCU_CFG0 |= RCU_APB1_CKAHB_DIV2;
    
    /* select HXTAL as system clock */
    RCU_CFG0 &= ~RCU_CFG0_SCS;
    RCU_CFG0 |= RCU_CKSYSSRC_HXTAL;
    
    /* wait until HXTAL is selected as system clock */
    while(RCU_SCSS_HXTAL != (RCU_CFG0 & RCU_CFG0_SCSS)){
    }
}

#elif defined (__SYSTEM_CLOCK_24M_PLL_HXTAL)
/*!
    \brief      configure the system clock to 24M by PLL which selects HXTAL(MD/HD/XD:8M; CL:25M) as its clock source
    \param[in]  none
    \param[out] none
    \retval     none
*/
static void system_clock_24m_hxtal(void)
{
    uint32_t timeout = 0U;
    uint32_t stab_flag = 0U;

    /* enable HXTAL */
    RCU_CTL |= RCU_CTL_HXTALEN;

    /* wait until HXTAL is stable or the startup time is longer than HXTAL_STARTUP_TIMEOUT */
    do{
        timeout++;
        stab_flag = (RCU_CTL & RCU_CTL_HXTALSTB);
    }while((0U == stab_flag) && (HXTAL_STARTUP_TIMEOUT != timeout));

    /* if fail */
    if(0U == (RCU_CTL & RCU_CTL_HXTALSTB)){
        while(1){
        }
    }

    /* HXTAL is stable */
    /* AHB = SYSCLK */
    RCU_CFG0 |= RCU_AHB_CKSYS_DIV1;
    /* APB2 = AHB/1 */
    RCU_CFG0 |= RCU_APB2_CKAHB_DIV1;
    /* APB1 = AHB/2 */
    RCU_CFG0 |= RCU_APB1_CKAHB_DIV2;

#if (defined(GD32F10X_MD) || defined(GD32F10X_HD) || defined(GD32F10X_XD))
    /* select HXTAL/2 as clock source */
    RCU_CFG0 &= ~(RCU_CFG0_PLLSEL | RCU_CFG0_PREDV0);
    RCU_CFG0 |= (RCU_PLLSRC_HXTAL | RCU_CFG0_PREDV0);

    /* CK_PLL = (CK_HXTAL/2) * 6 = 24 MHz */
    RCU_CFG0 &= ~(RCU_CFG0_PLLMF | RCU_CFG0_PLLMF_4);
    RCU_CFG0 |= RCU_PLL_MUL6;

#elif defined(GD32F10X_CL)
    /* CK_PLL = (CK_PREDIV0) * 6 = 24 MHz */
    RCU_CFG0 &= ~(RCU_CFG0_PLLMF | RCU_CFG0_PLLMF_4);
    RCU_CFG0 |= (RCU_PLLSRC_HXTAL | RCU_PLL_MUL6);

    /* CK_PREDIV0 = (CK_HXTAL)/5 *8 /10 = 4 MHz */
    RCU_CFG1 &= ~(RCU_CFG1_PREDV0SEL | RCU_CFG1_PLL1MF | RCU_CFG1_PREDV1 | RCU_CFG1_PREDV0);
    RCU_CFG1 |= (RCU_PREDV0SRC_CKPLL1 | RCU_PLL1_MUL8 | RCU_PREDV1_DIV5 | RCU_PREDV0_DIV10);

    /* enable PLL1 */
    RCU_CTL |= RCU_CTL_PLL1EN;
    /* wait till PLL1 is ready */
    while((RCU_CTL & RCU_CTL_PLL1STB) == 0){
    }
#endif /* GD32F10X_MD and GD32F10X_HD and GD32F10X_XD */

    /* enable PLL */
    RCU_CTL |= RCU_CTL_PLLEN;

    /* wait until PLL is stable */
    while(0U == (RCU_CTL & RCU_CTL_PLLSTB)){
    }

    /* select PLL as system clock */
    RCU_CFG0 &= ~RCU_CFG0_SCS;
    RCU_CFG0 |= RCU_CKSYSSRC_PLL;

    /* wait until PLL is selected as system clock */
    while(RCU_SCSS_PLL != (RCU_CFG0 & RCU_CFG0_SCSS)){
    }
}

#elif defined (__SYSTEM_CLOCK_36M_PLL_HXTAL)
/*!
    \brief      configure the system clock to 36M by PLL which selects HXTAL(MD/HD/XD:8M; CL:25M) as its clock source
    \param[in]  none
    \param[out] none
    \retval     none
*/
static void system_clock_36m_hxtal(void)
{
    uint32_t timeout = 0U;
    uint32_t stab_flag = 0U;

    /* enable HXTAL */
    RCU_CTL |= RCU_CTL_HXTALEN;

    /* wait until HXTAL is stable or the startup time is longer than HXTAL_STARTUP_TIMEOUT */
    do{
        timeout++;
        stab_flag = (RCU_CTL & RCU_CTL_HXTALSTB);
    }while((0U == stab_flag) && (HXTAL_STARTUP_TIMEOUT != timeout));

    /* if fail */
    if(0U == (RCU_CTL & RCU_CTL_HXTALSTB)){
        while(1){
        }
    }

    /* HXTAL is stable */
    /* AHB = SYSCLK */
    RCU_CFG0 |= RCU_AHB_CKSYS_DIV1;
    /* APB2 = AHB/1 */
    RCU_CFG0 |= RCU_APB2_CKAHB_DIV1;
    /* APB1 = AHB/2 */
    RCU_CFG0 |= RCU_APB1_CKAHB_DIV2;

#if (defined(GD32F10X_MD) || defined(GD32F10X_HD) || defined(GD32F10X_XD))
    /* select HXTAL/2 as clock source */
    RCU_CFG0 &= ~(RCU_CFG0_PLLSEL | RCU_CFG0_PREDV0);
    RCU_CFG0 |= (RCU_PLLSRC_HXTAL | RCU_CFG0_PREDV0);

    /* CK_PLL = (CK_HXTAL/2) * 9 = 36 MHz */
    RCU_CFG0 &= ~(RCU_CFG0_PLLMF | RCU_CFG0_PLLMF_4);
    RCU_CFG0 |= RCU_PLL_MUL9;

#elif defined(GD32F10X_CL)
    /* CK_PLL = (CK_PREDIV0) * 9 = 36 MHz */
    RCU_CFG0 &= ~(RCU_CFG0_PLLMF | RCU_CFG0_PLLMF_4);
    RCU_CFG0 |= (RCU_PLLSRC_HXTAL | RCU_PLL_MUL9);

    /* CK_PREDIV0 = (CK_HXTAL)/5 *8 /10 = 4 MHz */
    RCU_CFG1 &= ~(RCU_CFG1_PREDV0SEL | RCU_CFG1_PLL1MF | RCU_CFG1_PREDV1 | RCU_CFG1_PREDV0);
    RCU_CFG1 |= (RCU_PREDV0SRC_CKPLL1 | RCU_PLL1_MUL8 | RCU_PREDV1_DIV5 | RCU_PREDV0_DIV10);

    /* enable PLL1 */
    RCU_CTL |= RCU_CTL_PLL1EN;
    /* wait till PLL1 is ready */
    while((RCU_CTL & RCU_CTL_PLL1STB) == 0){
    }
#endif /* GD32F10X_MD and GD32F10X_HD and GD32F10X_XD */

    /* enable PLL */
    RCU_CTL |= RCU_CTL_PLLEN;

    /* wait until PLL is stable */
    while(0U == (RCU_CTL & RCU_CTL_PLLSTB)){
    }

    /* select PLL as system clock */
    RCU_CFG0 &= ~RCU_CFG0_SCS;
    RCU_CFG0 |= RCU_CKSYSSRC_PLL;

    /* wait until PLL is selected as system clock */
    while(RCU_SCSS_PLL != (RCU_CFG0 & RCU_CFG0_SCSS)){
    }
}

#elif defined (__SYSTEM_CLOCK_48M_PLL_HXTAL)
/*!
    \brief      configure the system clock to 48M by PLL which selects HXTAL(MD/HD/XD:8M; CL:25M) as its clock source
    \param[in]  none
    \param[out] none
    \retval     none
*/
static void system_clock_48m_hxtal(void)
{
    uint32_t timeout = 0U;
    uint32_t stab_flag = 0U;

    /* enable HXTAL */
    RCU_CTL |= RCU_CTL_HXTALEN;

    /* wait until HXTAL is stable or the startup time is longer than HXTAL_STARTUP_TIMEOUT */
    do{
        timeout++;
        stab_flag = (RCU_CTL & RCU_CTL_HXTALSTB);
    }while((0U == stab_flag) && (HXTAL_STARTUP_TIMEOUT != timeout));

    /* if fail */
    if(0U == (RCU_CTL & RCU_CTL_HXTALSTB)){
        while(1){
        }
    }

    /* HXTAL is stable */
    /* AHB = SYSCLK */
    RCU_CFG0 |= RCU_AHB_CKSYS_DIV1;
    /* APB2 = AHB/1 */
    RCU_CFG0 |= RCU_APB2_CKAHB_DIV1;
    /* APB1 = AHB/2 */
    RCU_CFG0 |= RCU_APB1_CKAHB_DIV2;

#if (defined(GD32F10X_MD) || defined(GD32F10X_HD) || defined(GD32F10X_XD))
    /* select HXTAL/2 as clock source */
    RCU_CFG0 &= ~(RCU_CFG0_PLLSEL | RCU_CFG0_PREDV0);
    RCU_CFG0 |= (RCU_PLLSRC_HXTAL | RCU_CFG0_PREDV0);

    /* CK_PLL = (CK_HXTAL/2) * 12 = 48 MHz */
    RCU_CFG0 &= ~(RCU_CFG0_PLLMF | RCU_CFG0_PLLMF_4);
    RCU_CFG0 |= RCU_PLL_MUL12;

#elif defined(GD32F10X_CL)
    /* CK_PLL = (CK_PREDIV0) * 12 = 48 MHz */
    RCU_CFG0 &= ~(RCU_CFG0_PLLMF | RCU_CFG0_PLLMF_4);
    RCU_CFG0 |= (RCU_PLLSRC_HXTAL | RCU_PLL_MUL12);

    /* CK_PREDIV0 = (CK_HXTAL)/5 *8 /10 = 4 MHz */
    RCU_CFG1 &= ~(RCU_CFG1_PREDV0SEL | RCU_CFG1_PLL1MF | RCU_CFG1_PREDV1 | RCU_CFG1_PREDV0);
    RCU_CFG1 |= (RCU_PREDV0SRC_CKPLL1 | RCU_PLL1_MUL8 | RCU_PREDV1_DIV5 | RCU_PREDV0_DIV10);

    /* enable PLL1 */
    RCU_CTL |= RCU_CTL_PLL1EN;
    /* wait till PLL1 is ready */
    while((RCU_CTL & RCU_CTL_PLL1STB) == 0){
    }
#endif /* GD32F10X_MD and GD32F10X_HD and GD32F10X_XD */

    /* enable PLL */
    RCU_CTL |= RCU_CTL_PLLEN;

    /* wait until PLL is stable */
    while(0U == (RCU_CTL & RCU_CTL_PLLSTB)){
    }

    /* select PLL as system clock */
    RCU_CFG0 &= ~RCU_CFG0_SCS;
    RCU_CFG0 |= RCU_CKSYSSRC_PLL;

    /* wait until PLL is selected as system clock */
    while(RCU_SCSS_PLL != (RCU_CFG0 & RCU_CFG0_SCSS)){
    }
}

#elif defined (__SYSTEM_CLOCK_56M_PLL_HXTAL)
/*!
    \brief      configure the system clock to 56M by PLL which selects HXTAL(MD/HD/XD:8M; CL:25M) as its clock source
    \param[in]  none
    \param[out] none
    \retval     none
*/
static void system_clock_56m_hxtal(void)
{
    uint32_t timeout = 0U;
    uint32_t stab_flag = 0U;

    /* enable HXTAL */
    RCU_CTL |= RCU_CTL_HXTALEN;

    /* wait until HXTAL is stable or the startup time is longer than HXTAL_STARTUP_TIMEOUT */
    do{
        timeout++;
        stab_flag = (RCU_CTL & RCU_CTL_HXTALSTB);
    }while((0U == stab_flag) && (HXTAL_STARTUP_TIMEOUT != timeout));

    /* if fail */
    if(0U == (RCU_CTL & RCU_CTL_HXTALSTB)){
        while(1){
        }
    }

    /* HXTAL is stable */
    /* AHB = SYSCLK */
    RCU_CFG0 |= RCU_AHB_CKSYS_DIV1;
    /* APB2 = AHB/1 */
    RCU_CFG0 |= RCU_APB2_CKAHB_DIV1;
    /* APB1 = AHB/2 */
    RCU_CFG0 |= RCU_APB1_CKAHB_DIV2;

#if (defined(GD32F10X_MD) || defined(GD32F10X_HD) || defined(GD32F10X_XD))
    /* select HXTAL/2 as clock source */
    RCU_CFG0 &= ~(RCU_CFG0_PLLSEL | RCU_CFG0_PREDV0);
    RCU_CFG0 |= (RCU_PLLSRC_HXTAL | RCU_CFG0_PREDV0);

    /* CK_PLL = (CK_HXTAL/2) * 14 = 56 MHz */
    RCU_CFG0 &= ~(RCU_CFG0_PLLMF | RCU_CFG0_PLLMF_4);
    RCU_CFG0 |= RCU_PLL_MUL14;

#elif defined(GD32F10X_CL)
    /* CK_PLL = (CK_PREDIV0) * 14 = 56 MHz */
    RCU_CFG0 &= ~(RCU_CFG0_PLLMF | RCU_CFG0_PLLMF_4);
    RCU_CFG0 |= (RCU_PLLSRC_HXTAL | RCU_PLL_MUL14);

    /* CK_PREDIV0 = (CK_HXTAL)/5 *8 /10 = 4 MHz */
    RCU_CFG1 &= ~(RCU_CFG1_PREDV0SEL | RCU_CFG1_PLL1MF | RCU_CFG1_PREDV1 | RCU_CFG1_PREDV0);
    RCU_CFG1 |= (RCU_PREDV0SRC_CKPLL1 | RCU_PLL1_MUL8 | RCU_PREDV1_DIV5 | RCU_PREDV0_DIV10);

    /* enable PLL1 */
    RCU_CTL |= RCU_CTL_PLL1EN;
    /* wait till PLL1 is ready */
    while((RCU_CTL & RCU_CTL_PLL1STB) == 0){
    }
#endif /* GD32F10X_MD and GD32F10X_HD and GD32F10X_XD */

    /* enable PLL */
    RCU_CTL |= RCU_CTL_PLLEN;

    /* wait until PLL is stable */
    while(0U == (RCU_CTL & RCU_CTL_PLLSTB)){
    }

    /* select PLL as system clock */
    RCU_CFG0 &= ~RCU_CFG0_SCS;
    RCU_CFG0 |= RCU_CKSYSSRC_PLL;

    /* wait until PLL is selected as system clock */
    while(RCU_SCSS_PLL != (RCU_CFG0 & RCU_CFG0_SCSS)){
    }
}

#elif defined (__SYSTEM_CLOCK_72M_PLL_HXTAL)
/*!
    \brief      configure the system clock to 72M by PLL which selects HXTAL(MD/HD/XD:8M; CL:25M) as its clock source
    \param[in]  none
    \param[out] none
    \retval     none
*/
static void system_clock_72m_hxtal(void)
{
    uint32_t timeout = 0U;
    uint32_t stab_flag = 0U;

    /* enable HXTAL */
    RCU_CTL |= RCU_CTL_HXTALEN;

    /* wait until HXTAL is stable or the startup time is longer than HXTAL_STARTUP_TIMEOUT */
    do{
        timeout++;
        stab_flag = (RCU_CTL & RCU_CTL_HXTALSTB);
    }while((0U == stab_flag) && (HXTAL_STARTUP_TIMEOUT != timeout));

    /* if fail */
    if(0U == (RCU_CTL & RCU_CTL_HXTALSTB)){
        while(1){
        }
    }

    /* HXTAL is stable */
    /* AHB = SYSCLK */
    RCU_CFG0 |= RCU_AHB_CKSYS_DIV1;
    /* APB2 = AHB/1 */
    RCU_CFG0 |= RCU_APB2_CKAHB_DIV1;
    /* APB1 = AHB/2 */
    RCU_CFG0 |= RCU_APB1_CKAHB_DIV2;

#if (defined(GD32F10X_MD) || defined(GD32F10X_HD) || defined(GD32F10X_XD))
    /* select HXTAL/2 as clock source */
    RCU_CFG0 &= ~(RCU_CFG0_PLLSEL | RCU_CFG0_PREDV0);
    RCU_CFG0 |= (RCU_PLLSRC_HXTAL | RCU_CFG0_PREDV0);

    /* CK_PLL = (CK_HXTAL/2) * 18 = 72 MHz */
    RCU_CFG0 &= ~(RCU_CFG0_PLLMF | RCU_CFG0_PLLMF_4);
    RCU_CFG0 |= RCU_PLL_MUL18;

#elif defined(GD32F10X_CL)
    /* CK_PLL = (CK_PREDIV0) * 18 = 72 MHz */ 
    RCU_CFG0 &= ~(RCU_CFG0_PLLMF | RCU_CFG0_PLLMF_4);
    RCU_CFG0 |= (RCU_PLLSRC_HXTAL | RCU_PLL_MUL18);

    /* CK_PREDIV0 = (CK_HXTAL)/5 *8 /10 = 4 MHz */ 
    RCU_CFG1 &= ~(RCU_CFG1_PREDV0SEL | RCU_CFG1_PLL1MF | RCU_CFG1_PREDV1 | RCU_CFG1_PREDV0);
    RCU_CFG1 |= (RCU_PREDV0SRC_CKPLL1 | RCU_PLL1_MUL8 | RCU_PREDV1_DIV5 | RCU_PREDV0_DIV10);

    /* enable PLL1 */
    RCU_CTL |= RCU_CTL_PLL1EN;
    /* wait till PLL1 is ready */
    while((RCU_CTL & RCU_CTL_PLL1STB) == 0){
    }
#endif /* GD32F10X_MD and GD32F10X_HD and GD32F10X_XD */

    /* enable PLL */
    RCU_CTL |= RCU_CTL_PLLEN;

    /* wait until PLL is stable */
    while(0U == (RCU_CTL & RCU_CTL_PLLSTB)){
    }

    /* select PLL as system clock */
    RCU_CFG0 &= ~RCU_CFG0_SCS;
    RCU_CFG0 |= RCU_CKSYSSRC_PLL;

    /* wait until PLL is selected as system clock */
    while(RCU_SCSS_PLL != (RCU_CFG0 & RCU_CFG0_SCSS)){
    }
}

#elif defined (__SYSTEM_CLOCK_96M_PLL_HXTAL)
/*!
    \brief      configure the system clock to 96M by PLL which selects HXTAL(MD/HD/XD:8M; CL:25M) as its clock source
    \param[in]  none
    \param[out] none
    \retval     none
*/
static void system_clock_96m_hxtal(void)
{
    uint32_t timeout = 0U;
    uint32_t stab_flag = 0U;

    /* enable HXTAL */
    RCU_CTL |= RCU_CTL_HXTALEN;

    /* wait until HXTAL is stable or the startup time is longer than HXTAL_STARTUP_TIMEOUT */
    do{
        timeout++;
        stab_flag = (RCU_CTL & RCU_CTL_HXTALSTB);
    }while((0U == stab_flag) && (HXTAL_STARTUP_TIMEOUT != timeout));

    /* if fail */
    if(0U == (RCU_CTL & RCU_CTL_HXTALSTB)){
        while(1){
        }
    }

    /* HXTAL is stable */
    /* AHB = SYSCLK */
    RCU_CFG0 |= RCU_AHB_CKSYS_DIV1;
    /* APB2 = AHB/1 */
    RCU_CFG0 |= RCU_APB2_CKAHB_DIV1;
    /* APB1 = AHB/2 */
    RCU_CFG0 |= RCU_APB1_CKAHB_DIV2;

#if (defined(GD32F10X_MD) || defined(GD32F10X_HD) || defined(GD32F10X_XD))
    /* select HXTAL/2 as clock source */
    RCU_CFG0 &= ~(RCU_CFG0_PLLSEL | RCU_CFG0_PREDV0);
    RCU_CFG0 |= (RCU_PLLSRC_HXTAL | RCU_CFG0_PREDV0);

    /* CK_PLL = (CK_HXTAL/2) * 24 = 96 MHz */
    RCU_CFG0 &= ~(RCU_CFG0_PLLMF | RCU_CFG0_PLLMF_4);
    RCU_CFG0 |= RCU_PLL_MUL24;

#elif defined(GD32F10X_CL)
    /* CK_PLL = (CK_PREDIV0) * 24 = 96 MHz */
    RCU_CFG0 &= ~(RCU_CFG0_PLLMF | RCU_CFG0_PLLMF_4);
    RCU_CFG0 |= (RCU_PLLSRC_HXTAL | RCU_PLL_MUL24);

    /* CK_PREDIV0 = (CK_HXTAL)/5 *8 /10 = 4 MHz */
    RCU_CFG1 &= ~(RCU_CFG1_PREDV0SEL | RCU_CFG1_PLL1MF | RCU_CFG1_PREDV1 | RCU_CFG1_PREDV0);
    RCU_CFG1 |= (RCU_PREDV0SRC_CKPLL1 | RCU_PLL1_MUL8 | RCU_PREDV1_DIV5 | RCU_PREDV0_DIV10);

    /* enable PLL1 */
    RCU_CTL |= RCU_CTL_PLL1EN;
    /* wait till PLL1 is ready */
    while((RCU_CTL & RCU_CTL_PLL1STB) == 0){
    }
#endif /* GD32F10X_MD and GD32F10X_HD and GD32F10X_XD */

    /* enable PLL */
    RCU_CTL |= RCU_CTL_PLLEN;

    /* wait until PLL is stable */
    while(0U == (RCU_CTL & RCU_CTL_PLLSTB)){
    }

    /* select PLL as system clock */
    RCU_CFG0 &= ~RCU_CFG0_SCS;
    RCU_CFG0 |= RCU_CKSYSSRC_PLL;

    /* wait until PLL is selected as system clock */
    while(RCU_SCSS_PLL != (RCU_CFG0 & RCU_CFG0_SCSS)){
    }
}

#elif defined (__SYSTEM_CLOCK_108M_PLL_HXTAL)
/*!
    \brief      configure the system clock to 108M by PLL which selects HXTAL(MD/HD/XD:8M; CL:25M) as its clock source
    \param[in]  none
    \param[out] none
    \retval     none
*/
static void system_clock_108m_hxtal(void)
{
    uint32_t timeout   = 0U;
    uint32_t stab_flag = 0U;

    /* enable HXTAL */
    RCU_CTL |= RCU_CTL_HXTALEN;

    /* wait until HXTAL is stable or the startup time is longer than HXTAL_STARTUP_TIMEOUT */
    do{
        timeout++;
        stab_flag = (RCU_CTL & RCU_CTL_HXTALSTB);
    }while((0U == stab_flag) && (HXTAL_STARTUP_TIMEOUT != timeout));

    /* if fail */
    if(0U == (RCU_CTL & RCU_CTL_HXTALSTB)){
        while(1){
        }
    }

    /* HXTAL is stable */
    /* AHB = SYSCLK */
    RCU_CFG0 |= RCU_AHB_CKSYS_DIV1;
    /* APB2 = AHB/1 */
    RCU_CFG0 |= RCU_APB2_CKAHB_DIV1;
    /* APB1 = AHB/2 */
    RCU_CFG0 |= RCU_APB1_CKAHB_DIV2;

#if (defined(GD32F10X_MD) || defined(GD32F10X_HD) || defined(GD32F10X_XD))
    /* select HXTAL/2 as clock source */
    RCU_CFG0 &= ~(RCU_CFG0_PLLSEL | RCU_CFG0_PREDV0);
    RCU_CFG0 |= (RCU_PLLSRC_HXTAL | RCU_CFG0_PREDV0);

    /* CK_PLL = (CK_HXTAL/2) * 27 = 108 MHz */
    RCU_CFG0 &= ~(RCU_CFG0_PLLMF | RCU_CFG0_PLLMF_4);
    RCU_CFG0 |= RCU_PLL_MUL27;

#elif defined(GD32F10X_CL)
    /* CK_PLL = (CK_PREDIV0) * 27 = 108 MHz */ 
    RCU_CFG0 &= ~(RCU_CFG0_PLLMF | RCU_CFG0_PLLMF_4);
    RCU_CFG0 |= (RCU_PLLSRC_HXTAL | RCU_PLL_MUL27);

    /* CK_PREDIV0 = (CK_HXTAL)/5 *8 /10 = 4 MHz */ 
    RCU_CFG1 &= ~(RCU_CFG1_PREDV0SEL | RCU_CFG1_PLL1MF | RCU_CFG1_PREDV1 | RCU_CFG1_PREDV0);
    RCU_CFG1 |= (RCU_PREDV0SRC_CKPLL1 | RCU_PLL1_MUL8 | RCU_PREDV1_DIV5 | RCU_PREDV0_DIV10);

    /* enable PLL1 */
    RCU_CTL |= RCU_CTL_PLL1EN;
    /* wait till PLL1 is ready */
    while(0U == (RCU_CTL & RCU_CTL_PLL1STB)){
    }
#endif /* GD32F10X_MD and GD32F10X_HD and GD32F10X_XD */

    /* enable PLL */
    RCU_CTL |= RCU_CTL_PLLEN;

    /* wait until PLL is stable */
    while(0U == (RCU_CTL & RCU_CTL_PLLSTB)){
    }

    /* select PLL as system clock */
    RCU_CFG0 &= ~RCU_CFG0_SCS;
    RCU_CFG0 |= RCU_CKSYSSRC_PLL;

    /* wait until PLL is selected as system clock */
    while(RCU_SCSS_PLL != (RCU_CFG0 & RCU_CFG0_SCSS)){
    }
}

#elif defined (__SYSTEM_CLOCK_48M_PLL_IRC8M)
/*!
    \brief      configure the system clock to 48M by PLL which selects IRC8M as its clock source
    \param[in]  none
    \param[out] none
    \retval     none
*/
static void system_clock_48m_irc8m(void)
{
    uint32_t timeout = 0U;
    uint32_t stab_flag = 0U;
    
    /* enable IRC8M */
    RCU_CTL |= RCU_CTL_IRC8MEN;

    /* wait until IRC8M is stable or the startup time is longer than IRC8M_STARTUP_TIMEOUT */
    do{
        timeout++;
        stab_flag = (RCU_CTL & RCU_CTL_IRC8MSTB);
    }
    while((0U == stab_flag) && (IRC8M_STARTUP_TIMEOUT != timeout));

    /* if fail */
    if(0U == (RCU_CTL & RCU_CTL_IRC8MSTB)){
      while(1){
      }
    }

    /* IRC8M is stable */
    /* AHB = SYSCLK */
    RCU_CFG0 |= RCU_AHB_CKSYS_DIV1;
    /* APB2 = AHB/1 */
    RCU_CFG0 |= RCU_APB2_CKAHB_DIV1;
    /* APB1 = AHB/2 */
    RCU_CFG0 |= RCU_APB1_CKAHB_DIV2;

    /* CK_PLL = (CK_IRC8M/2) * 12 = 48 MHz */
    RCU_CFG0 &= ~(RCU_CFG0_PLLMF | RCU_CFG0_PLLMF_4);
    RCU_CFG0 |= RCU_PLL_MUL12;

    /* enable PLL */
    RCU_CTL |= RCU_CTL_PLLEN;

    /* wait until PLL is stable */
    while(0U == (RCU_CTL & RCU_CTL_PLLSTB)){
    }

    /* select PLL as system clock */
    RCU_CFG0 &= ~RCU_CFG0_SCS;
    RCU_CFG0 |= RCU_CKSYSSRC_PLL;

    /* wait until PLL is selected as system clock */
    while(RCU_SCSS_PLL != (RCU_CFG0 & RCU_CFG0_SCSS)){
    }
}

#elif defined (__SYSTEM_CLOCK_72M_PLL_IRC8M)
/*!
    \brief      configure the system clock to 72M by PLL which selects IRC8M as its clock source
    \param[in]  none
    \param[out] none
    \retval     none
*/
static void system_clock_72m_irc8m(void)
{
    uint32_t timeout = 0U;
    uint32_t stab_flag = 0U;
    
    /* enable IRC8M */
    RCU_CTL |= RCU_CTL_IRC8MEN;

    /* wait until IRC8M is stable or the startup time is longer than IRC8M_STARTUP_TIMEOUT */
    do{
        timeout++;
        stab_flag = (RCU_CTL & RCU_CTL_IRC8MSTB);
    }
    while((0U == stab_flag) && (IRC8M_STARTUP_TIMEOUT != timeout));

    /* if fail */
    if(0U == (RCU_CTL & RCU_CTL_IRC8MSTB)){
      while(1){
      }
    }

    /* IRC8M is stable */
    /* AHB = SYSCLK */
    RCU_CFG0 |= RCU_AHB_CKSYS_DIV1;
    /* APB2 = AHB/1 */
    RCU_CFG0 |= RCU_APB2_CKAHB_DIV1;
    /* APB1 = AHB/2 */
    RCU_CFG0 |= RCU_APB1_CKAHB_DIV2;

    /* CK_PLL = (CK_IRC8M/2) * 18 = 72 MHz */
    RCU_CFG0 &= ~(RCU_CFG0_PLLMF | RCU_CFG0_PLLMF_4);
    RCU_CFG0 |= RCU_PLL_MUL18;

    /* enable PLL */
    RCU_CTL |= RCU_CTL_PLLEN;

    /* wait until PLL is stable */
    while(0U == (RCU_CTL & RCU_CTL_PLLSTB)){
    }

    /* select PLL as system clock */
    RCU_CFG0 &= ~RCU_CFG0_SCS;
    RCU_CFG0 |= RCU_CKSYSSRC_PLL;

    /* wait until PLL is selected as system clock */
    while(RCU_SCSS_PLL != (RCU_CFG0 & RCU_CFG0_SCSS)){
    }
}

#elif defined (__SYSTEM_CLOCK_108M_PLL_IRC8M)
/*!
    \brief      configure the system clock to 108M by PLL which selects IRC8M as its clock source
    \param[in]  none
    \param[out] none
    \retval     none
*/
static void system_clock_108m_irc8m(void)
{
    uint32_t timeout = 0U;
    uint32_t stab_flag = 0U;
    
    /* enable IRC8M */
    RCU_CTL |= RCU_CTL_IRC8MEN;

    /* wait until IRC8M is stable or the startup time is longer than IRC8M_STARTUP_TIMEOUT */
    do{
        timeout++;
        stab_flag = (RCU_CTL & RCU_CTL_IRC8MSTB);
    }
    while((0U == stab_flag) && (IRC8M_STARTUP_TIMEOUT != timeout));

    /* if fail */
    if(0U == (RCU_CTL & RCU_CTL_IRC8MSTB)){
      while(1){
      }
    }

    /* IRC8M is stable */
    /* AHB = SYSCLK */
    RCU_CFG0 |= RCU_AHB_CKSYS_DIV1;
    /* APB2 = AHB/1 */
    RCU_CFG0 |= RCU_APB2_CKAHB_DIV1;
    /* APB1 = AHB/2 */
    RCU_CFG0 |= RCU_APB1_CKAHB_DIV2;

    /* CK_PLL = (CK_IRC8M/2) * 27 = 108 MHz */
    RCU_CFG0 &= ~(RCU_CFG0_PLLMF | RCU_CFG0_PLLMF_4);
    RCU_CFG0 |= RCU_PLL_MUL27;

    /* enable PLL */
    RCU_CTL |= RCU_CTL_PLLEN;

    /* wait until PLL is stable */
    while(0U == (RCU_CTL & RCU_CTL_PLLSTB)){
    }

    /* select PLL as system clock */
    RCU_CFG0 &= ~RCU_CFG0_SCS;
    RCU_CFG0 |= RCU_CKSYSSRC_PLL;

    /* wait until PLL is selected as system clock */
    while(RCU_SCSS_PLL != (RCU_CFG0 & RCU_CFG0_SCSS)){
    }
}

/*!
    \brief      update the SystemCoreClock with current core clock retrieved from cpu registers
    \param[in]  none
    \param[out] none
    \retval     none
*/
void SystemCoreClockUpdate(void)
{
    uint32_t scss;
    uint32_t pllsel, predv0sel, pllmf, ck_src, idx, clk_exp;
#ifdef  GD32F10X_CL
    uint32_t predv0, predv1, pll1mf;
#endif /* GD32F10X_CL */
    /* exponent of AHB, APB1 and APB2 clock divider */
    const uint8_t ahb_exp[16] = {0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 3, 4, 6, 7, 8, 9};

    scss = GET_BITS(RCU_CFG0, 2, 3);

    switch (scss)
    {
        /* IRC8M is selected as CK_SYS */
        case SEL_IRC8M:
            SystemCoreClock = IRC8M_VALUE;
            break;
            
        /* HXTAL is selected as CK_SYS */
        case SEL_HXTAL:
            SystemCoreClock = HXTAL_VALUE;
            break;
            
        /* PLL is selected as CK_SYS */
        case SEL_PLL:
            /* PLL clock source selection, HXTAL or IRC8M/2 */
            pllsel = (RCU_CFG0 & RCU_CFG0_PLLSEL);

            if(RCU_PLLSRC_IRC8M_DIV2 == pllsel){
                /* PLL clock source is IRC8M/2 */
                ck_src = IRC8M_VALUE / 2U;
            }else{
                /* PLL clock source is HXTAL */
                ck_src = HXTAL_VALUE;
            
#if (defined(GD32F10X_MD) || defined(GD32F10X_HD) || defined(GD32F10X_XD))
                predv0sel = (RCU_CFG0 & RCU_CFG0_PREDV0);

                /* PREDV0 input source clock divided by 2 */
                if(RCU_CFG0_PREDV0 == predv0sel){
                    ck_src = HXTAL_VALUE / 2U;
                }
#elif defined(GD32F10X_CL)
                predv0sel = (RCU_CFG1 & RCU_CFG1_PREDV0SEL);

                /* source clock use PLL1 */
                if(RCU_PREDV0SRC_CKPLL1 == predv0sel){
                    predv1 = ((RCU_CFG1 & RCU_CFG1_PREDV1) >> 4) + 1U;
                    pll1mf = ((RCU_CFG1 & RCU_CFG1_PLL1MF) >> 8) + 2U;
                    if(17U == pll1mf){
                        pll1mf = 20U;
                    }
                    ck_src = (ck_src / predv1) * pll1mf;
                }
                predv0 = (RCU_CFG1 & RCU_CFG1_PREDV0) + 1U;
                ck_src /= predv0;
#endif /* GD32F10X_MD and GD32F10X_HD and GD32F10X_XD */
            }

            /* PLL multiplication factor */
            pllmf = GET_BITS(RCU_CFG0, 18, 21);

            if((RCU_CFG0 & RCU_CFG0_PLLMF_4)){
                pllmf |= 0x10U;
            }

            if(pllmf >= 15U){
                pllmf += 1U;
            }else{
                pllmf += 2U;
            }

            SystemCoreClock = ck_src * pllmf;

#ifdef GD32F10X_CL
            if(15U == pllmf){
                /* PLL source clock multiply by 6.5 */
                SystemCoreClock = ck_src * 6U + ck_src / 2U;
            }
#endif /* GD32F10X_CL */

            break;

        /* IRC8M is selected as CK_SYS */
        default:
            SystemCoreClock = IRC8M_VALUE;
            break;
    }
    /* calculate AHB clock frequency */
    idx = GET_BITS(RCU_CFG0, 4, 7);
    clk_exp = ahb_exp[idx];
    SystemCoreClock = SystemCoreClock >> clk_exp;
}
#endif
