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make SPI RX/TX dma startup be atomic #42

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Jun 17, 2022
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make SPI RX/TX dma startup be atomic #42

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14 changes: 9 additions & 5 deletions samd/dma.c
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Original file line number Diff line number Diff line change
Expand Up @@ -27,6 +27,7 @@

#include <string.h>

#include "mphalport.h"
#include "py/gc.h"
#include "py/mpstate.h"

Expand Down Expand Up @@ -66,6 +67,7 @@ void init_shared_dma(void) {

DMAC->CTRL.reg = DMAC_CTRL_DMAENABLE | DMAC_CTRL_LVLEN0;

// Non-audio channels will be configured on demand.
for (uint8_t i = 0; i < AUDIO_DMA_CHANNEL_COUNT; i++) {
dma_configure(i, 0, true);
}
Expand Down Expand Up @@ -155,15 +157,17 @@ static int32_t shared_dma_transfer(void* peripheral,
SercomSpi *s = &((Sercom*) peripheral)->SPI;
s->INTFLAG.reg = SERCOM_SPI_INTFLAG_RXC | SERCOM_SPI_INTFLAG_DRE;
}
// Start the RX job first so we don't miss the first byte. The TX job clocks
// the output.

// Start the RX job first so we don't miss the first byte. The TX job clocks the output.
// Disable interrupts during startup to make sure both RX and TX start at just about the same time.
mp_hal_disable_all_interrupts();
if (rx_active) {
dma_enable_channel(SHARED_RX_CHANNEL);
}
if (tx_active) {
dma_enable_channel(SHARED_TX_CHANNEL);
}

mp_hal_enable_all_interrupts();

if (!sercom) {
if (rx_active) {
Expand All @@ -177,7 +181,7 @@ static int32_t shared_dma_transfer(void* peripheral,
// legitimate state for a DMA channel to be in (apparently), so we can't use that alone as a check.
// Instead, let's look at the ACTIVE flag. When DMA is hung, everything in ACTIVE is zeros.
bool is_okay = false;
for (int i=0; i<10 && !is_okay; i++) {
for (int i = 0; i < 10 && !is_okay; i++) {
bool complete = true;
if (rx_active) {
if (DMAC->Channel[SHARED_RX_CHANNEL].CHSTATUS.reg & 0x3)
Expand All @@ -190,7 +194,7 @@ static int32_t shared_dma_transfer(void* peripheral,
is_okay = is_okay || (DMAC->ACTIVE.bit.ABUSY || complete);
}
if (!is_okay) {
for (int i=0; i<AUDIO_DMA_CHANNEL_COUNT; i++) {
for (int i = 0; i < AUDIO_DMA_CHANNEL_COUNT; i++) {
if(DMAC->Channel[i].CHCTRLA.bit.ENABLE) {
DMAC->Channel[i].CHCTRLA.bit.ENABLE = 0;
DMAC->Channel[i].CHCTRLA.bit.ENABLE = 1;
Expand Down