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stm32/powerctrl: Don't configure clocks if already at desired frequency.

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Configuring clocks is a critical operation and is best to avoid when
possible.  If the clocks really need to be reset to the same values then
one can pass in a slightly higher value, eg 168000001 Hz to get 168MHz.
This commit is contained in:
Damien George 2018-09-24 17:07:15 +10:00
parent bc54c57590
commit 6ea6c7cc9e
1 changed files with 8 additions and 0 deletions
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8
ports/stm32/powerctrl.c
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@ -128,6 +128,14 @@ STATIC uint32_t calc_apb_div(uint32_t wanted_div) {
}
int powerctrl_set_sysclk(uint32_t sysclk, uint32_t ahb, uint32_t apb1, uint32_t apb2) {
// Return straightaway if the clocks are already at the desired frequency
if (sysclk == HAL_RCC_GetSysClockFreq()
&& ahb == HAL_RCC_GetHCLKFreq()
&& apb1 == HAL_RCC_GetPCLK1Freq()
&& apb2 == HAL_RCC_GetPCLK2Freq()) {
return 0;
}
// Default PLL parameters that give 48MHz on PLL48CK
uint32_t m = HSE_VALUE / 1000000, n = 336, p = 2, q = 7;
uint32_t sysclk_source;