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stm32/timer: Make timer_get_source_freq more efficient by using regs.

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Use direct register access to get the APB clock divider.  This reduces code
size and makes the code more efficient.
This commit is contained in:
Damien George 2018-05-28 11:57:17 +10:00
parent 070937fe93
commit 5c0685912f
1 changed files with 15 additions and 13 deletions
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26
ports/stm32/timer.c
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@ -228,25 +228,27 @@ void HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef *htim) {
// APB clock. Otherwise (APB prescaler > 1) the timer clock is twice its
// respective APB clock. See DM00031020 Rev 4, page 115.
uint32_t timer_get_source_freq(uint32_t tim_id) {
uint32_t source;
uint32_t latency;
RCC_ClkInitTypeDef rcc_init;
// Get clock config.
HAL_RCC_GetClockConfig(&rcc_init, &latency);
uint32_t source, clk_div;
if (tim_id == 1 || (8 <= tim_id && tim_id <= 11)) {
// TIM{1,8,9,10,11} are on APB2
source = HAL_RCC_GetPCLK2Freq();
if (rcc_init.APB2CLKDivider != RCC_HCLK_DIV1) {
source *= 2;
}
#if defined(STM32H7)
clk_div = RCC->D2CFGR & RCC_D2CFGR_D2PPRE2;
#else
clk_div = RCC->CFGR & RCC_CFGR_PPRE2;
#endif
} else {
// TIM{2,3,4,5,6,7,12,13,14} are on APB1
source = HAL_RCC_GetPCLK1Freq();
if (rcc_init.APB1CLKDivider != RCC_HCLK_DIV1) {
source *= 2;
#if defined(STM32H7)
clk_div = RCC->D2CFGR & RCC_D2CFGR_D2PPRE1;
#else
clk_div = RCC->CFGR & RCC_CFGR_PPRE1;
#endif
}
if (clk_div != 0) {
// APB prescaler for this timer is > 1
source *= 2;
}
return source;
}