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stm32/sdcard: Make SD wait routine more power efficient by using WFI.

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Using WFI allows the CPU to sleep while it is waiting, reducing power
consumption.
This commit is contained in:
Damien George 2018-02-01 12:20:45 +11:00
parent c0496fd44d
commit fed1b4fb56
1 changed files with 11 additions and 1 deletions
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12
ports/stm32/sdcard.c
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@ -244,11 +244,20 @@ void SDMMC2_IRQHandler(void) {
STATIC HAL_StatusTypeDef sdcard_wait_finished(SD_HandleTypeDef *sd, uint32_t timeout) { STATIC HAL_StatusTypeDef sdcard_wait_finished(SD_HandleTypeDef *sd, uint32_t timeout) {
// Wait for HAL driver to be ready (eg for DMA to finish) // Wait for HAL driver to be ready (eg for DMA to finish)
uint32_t start = HAL_GetTick(); uint32_t start = HAL_GetTick();
while (sd->State == HAL_SD_STATE_BUSY) { for (;;) {
// Do an atomic check of the state; WFI will exit even if IRQs are disabled
uint32_t irq_state = disable_irq();
if (sd->State != HAL_SD_STATE_BUSY) {
enable_irq(irq_state);
break;
}
__WFI();
enable_irq(irq_state);
if (HAL_GetTick() - start >= timeout) { if (HAL_GetTick() - start >= timeout) {
return HAL_TIMEOUT; return HAL_TIMEOUT;
} }
} }
// Wait for SD card to complete the operation // Wait for SD card to complete the operation
for (;;) { for (;;) {
HAL_SD_CardStateTypedef state = HAL_SD_GetCardState(sd); HAL_SD_CardStateTypedef state = HAL_SD_GetCardState(sd);
@ -261,6 +270,7 @@ STATIC HAL_StatusTypeDef sdcard_wait_finished(SD_HandleTypeDef *sd, uint32_t tim
if (HAL_GetTick() - start >= timeout) { if (HAL_GetTick() - start >= timeout) {
return HAL_TIMEOUT; return HAL_TIMEOUT;
} }
__WFI();
} }
return HAL_OK; return HAL_OK;
} }