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// Code to setup clocks on stm32f4
//
// Copyright (C) 2019 Kevin O'Connor <kevin@koconnor.net>
//
// This file may be distributed under the terms of the GNU GPLv3 license.
#include "autoconf.h" // CONFIG_STM32F4_CLOCK_REF_8M
#include "internal.h" // enable_pclock
#define FREQ_PERIPH (CONFIG_CLOCK_FREQ / 4)
// Enable a peripheral clock
void
enable_pclock(uint32_t periph_base)
{
if (periph_base < APB2PERIPH_BASE) {
uint32_t pos = (periph_base - APB1PERIPH_BASE) / 0x400;
RCC->APB1ENR |= (1<<pos);
RCC->APB1ENR;
} else if (periph_base < AHB1PERIPH_BASE) {
uint32_t pos = (periph_base - APB2PERIPH_BASE) / 0x400;
RCC->APB2ENR |= (1<<pos);
RCC->APB2ENR;
} else if (periph_base < AHB2PERIPH_BASE) {
uint32_t pos = (periph_base - AHB1PERIPH_BASE) / 0x400;
RCC->AHB1ENR |= (1<<pos);
RCC->AHB1ENR;
}
}
// Return the frequency of the given peripheral clock
uint32_t
get_pclock_frequency(uint32_t periph_base)
{
return FREQ_PERIPH;
}
// Clock configuration
static void
enable_clock_stm32f40x(void)
{
#if CONFIG_MACH_STM32F405 || CONFIG_MACH_STM32F407
if (CONFIG_STM32F4_CLOCK_REF_8M) {
// Configure 168Mhz PLL from external 8Mhz crystal (HSE)
RCC->CR |= RCC_CR_HSEON;
RCC->PLLCFGR = (
RCC_PLLCFGR_PLLSRC_HSE | (4 << RCC_PLLCFGR_PLLM_Pos)
| (168 << RCC_PLLCFGR_PLLN_Pos) | (0 << RCC_PLLCFGR_PLLP_Pos)
| (7 << RCC_PLLCFGR_PLLQ_Pos));
} else {
// Configure 168Mhz PLL from internal 16Mhz oscillator (HSI)
RCC->PLLCFGR = (
RCC_PLLCFGR_PLLSRC_HSI | (8 << RCC_PLLCFGR_PLLM_Pos)
| (168 << RCC_PLLCFGR_PLLN_Pos) | (0 << RCC_PLLCFGR_PLLP_Pos)
| (7 << RCC_PLLCFGR_PLLQ_Pos));
}
RCC->CR |= RCC_CR_PLLON;
#endif
}
static void
enable_clock_stm32f446(void)
{
#if CONFIG_MACH_STM32F446
if (CONFIG_STM32F4_CLOCK_REF_8M) {
// Configure 180Mhz PLL from external 8Mhz crystal (HSE)
RCC->CR |= RCC_CR_HSEON;
RCC->PLLCFGR = (
RCC_PLLCFGR_PLLSRC_HSE | (4 << RCC_PLLCFGR_PLLM_Pos)
| (180 << RCC_PLLCFGR_PLLN_Pos) | (0 << RCC_PLLCFGR_PLLP_Pos)
| (7 << RCC_PLLCFGR_PLLQ_Pos) | (6 << RCC_PLLCFGR_PLLR_Pos));
} else {
// Configure 180Mhz PLL from internal 16Mhz oscillator (HSI)
RCC->PLLCFGR = (
RCC_PLLCFGR_PLLSRC_HSI | (8 << RCC_PLLCFGR_PLLM_Pos)
| (180 << RCC_PLLCFGR_PLLN_Pos) | (0 << RCC_PLLCFGR_PLLP_Pos)
| (7 << RCC_PLLCFGR_PLLQ_Pos) | (6 << RCC_PLLCFGR_PLLR_Pos));
}
RCC->CR |= RCC_CR_PLLON;
// Enable "over drive"
enable_pclock(PWR_BASE);
PWR->CR = (3 << PWR_CR_VOS_Pos) | PWR_CR_ODEN;
while (!(PWR->CSR & PWR_CSR_ODRDY))
;
PWR->CR = (3 << PWR_CR_VOS_Pos) | PWR_CR_ODEN | PWR_CR_ODSWEN;
while (!(PWR->CSR & PWR_CSR_ODSWRDY))
;
#endif
}
// Main clock setup called at chip startup
void
clock_setup(void)
{
if (CONFIG_MACH_STM32F405 || CONFIG_MACH_STM32F407)
enable_clock_stm32f40x();
else
enable_clock_stm32f446();
// Set flash latency
FLASH->ACR = (FLASH_ACR_LATENCY_5WS | FLASH_ACR_ICEN | FLASH_ACR_DCEN
| FLASH_ACR_PRFTEN);
// Wait for PLL lock
while (!(RCC->CR & RCC_CR_PLLRDY))
;
// Switch system clock to PLL
RCC->CFGR = RCC_CFGR_PPRE1_DIV4 | RCC_CFGR_PPRE2_DIV4 | RCC_CFGR_SW_PLL;
while ((RCC->CFGR & RCC_CFGR_SWS_Msk) != RCC_CFGR_SWS_PLL)
;
// Enable GPIO clocks
enable_pclock(GPIOA_BASE);
enable_pclock(GPIOB_BASE);
enable_pclock(GPIOC_BASE);
}
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