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stm32/powerctrl: For F7, allow PLLM!=HSE when setting PLLSAI to 48MHz.

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PLLM is shared among all PLL blocks on F7 MCUs, and this calculation to
configure PLLSAI to have 48MHz on the P output previously assumed that PLLM
is equal to HSE (eg PLLM=25 for HSE=25MHz).  This commit relaxes this
assumption to allow other values of PLLM.
This commit is contained in:
Damien George 2020-01-29 16:49:13 +11:00
parent c3095b37e9
commit a542c6d7e0
1 changed files with 3 additions and 1 deletions
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4
ports/stm32/powerctrl.c
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@ -94,9 +94,11 @@ int powerctrl_rcc_clock_config_pll(RCC_ClkInitTypeDef *rcc_init, uint32_t sysclk
if (need_pllsai) {
// Configure PLLSAI at 48MHz for those peripherals that need this freq
const uint32_t pllsain = 192;
// (calculation assumes it can get an integral value of PLLSAIN)
const uint32_t pllm = (RCC->PLLCFGR >> RCC_PLLCFGR_PLLM_Pos) & 0x3f;
const uint32_t pllsaip = 4;
const uint32_t pllsaiq = 2;
const uint32_t pllsain = 48 * pllsaip * pllm / (HSE_VALUE / 1000000);
RCC->PLLSAICFGR = pllsaiq << RCC_PLLSAICFGR_PLLSAIQ_Pos
| (pllsaip / 2 - 1) << RCC_PLLSAICFGR_PLLSAIP_Pos
| pllsain << RCC_PLLSAICFGR_PLLSAIN_Pos;