How to configure STM32F37x ARM Cortex M4 microcontroller to 72 MHz? (using 8 MHz crystal)

System_Configuration.cpp

//
// Clock STM32F37x to 72 MHz using 8 MHz crystal
//

#include <stm32f37x.h>

/*
AHB  = max 72 MHz
APB2 = max 72 MHz
APB1 = max 36 MHz

SysTick = AHB/8 OR AHB (configure from SysTick configuration bits)

Timers = 2x APB to which they are connected.

USART1/2/3 still needs to be configured. (RCC_CFGR3)
*/


void Configure_Clocks()
{
    // Flash = two wait states, as 48 < SYSCLK <= 72 MHz
    FLASH->ACR |= FLASH_ACR_LATENCY_1;

    // Turn HSE on
    RCC->CR |= RCC_CR_HSEON;
    while (!(RCC->CR & RCC_CR_HSERDY));

    // Turn PLL off
    RCC->CR &= ~RCC_CR_PLLON;
    while (RCC->CR & RCC_CR_PLLRDY);

    // Change PLL parameters
    RCC->CFGR |= RCC_CFGR_PLLSRC;         // Set HSE as PLL clock source
    RCC->CFGR |= RCC_CFGR_PLLMULL_0 |     // PLL input clock x 9 = 72 MHz
                 RCC_CFGR_PLLMULL_1 |
                 RCC_CFGR_PLLMULL_2;
    RCC->CFGR |= RCC_CFGR_MCO_PLL;        // MCO = PLL clock divided by 2 selected

    // Change bus clock prescaler parameters
    RCC->CFGR &= ~RCC_CFGR_PPRE2;         // APB2 = AHB clock not divided
    RCC->CFGR |= RCC_CFGR_PPRE1_DIV2;     // APB1 = AHB clock divided by 2
    RCC->CFGR &= ~RCC_CFGR_HPRE;          // AHB  = not divided

    // Turn PLL back on
    RCC->CR |= RCC_CR_PLLON;
    while (!(RCC->CR & RCC_CR_PLLRDY));

    // Switch system clock source to PLL
    RCC->CFGR |= RCC_CFGR_SW_PLL;
    while ((RCC->CFGR & RCC_CFGR_SWS_PLL) != RCC_CFGR_SWS_PLL);
}