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Audio related DMA cleanup #7274

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Audio related DMA cleanup #7274

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46 changes: 41 additions & 5 deletions radio/src/targets/common/arm/stm32/audio_dac_driver.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -102,6 +102,11 @@ void audioUnmute()
static uint16_t _dma_buffer[DMA_BUFFER_LEN] __DMA_NO_CACHE;

static volatile uint32_t _dma_buffer_offset = 0;
static volatile uint8_t _empty_dma_halves = 0;

// Require sustained silence before stopping DMA to avoid start/stop thrashing
// when the producer briefly lags behind the consumer.
constexpr uint8_t DMA_EMPTY_HALVES_STOP_THRESHOLD = 6;

static inline uint32_t _calc_offset(uint8_t tc)
{
Expand Down Expand Up @@ -166,16 +171,33 @@ static void dac_dma_init()
NVIC_SetPriority(AUDIO_DMA_Stream_IRQn, 7);
}

static inline void dac_clear_dma_flags()
{
// Drain stale half/complete flags so a new transfer starts from a clean state.
stm32_dma_check_ht_flag(AUDIO_DMA, AUDIO_DMA_Stream);
stm32_dma_check_tc_flag(AUDIO_DMA, AUDIO_DMA_Stream);
}

static void dac_close_dma_xfer()
{
LL_DMA_DisableIT_TC(AUDIO_DMA, AUDIO_DMA_Stream);
LL_DMA_DisableIT_HT(AUDIO_DMA, AUDIO_DMA_Stream);
// TODO: reset flags

LL_DMA_DisableStream(AUDIO_DMA, AUDIO_DMA_Stream);

// Wait until DMA EN bit is actually cleared by hardware.
uint32_t timeout = 1000;
while (LL_DMA_IsEnabledStream(AUDIO_DMA, AUDIO_DMA_Stream) && timeout--) {
__NOP();
}

dac_clear_dma_flags();
}

static void dac_start_dma()
{
dac_clear_dma_flags();

// enable DMA stream and transfer complete interrupt
LL_DMA_EnableIT_HT(AUDIO_DMA, AUDIO_DMA_Stream);
LL_DMA_EnableIT_TC(AUDIO_DMA, AUDIO_DMA_Stream);
Expand All @@ -192,6 +214,7 @@ void audioConsumeCurrentBuffer()
{
if (!LL_DMA_IsEnabledStream(AUDIO_DMA, AUDIO_DMA_Stream)) {
if (!audio_update_dma_buffer(0)) {
_empty_dma_halves = 0;
#if defined(AUDIO_MUTE_GPIO)
audioUnmute();
#endif
Expand All @@ -206,16 +229,29 @@ void audioConsumeCurrentBuffer()

extern "C" void AUDIO_DMA_Stream_IRQHandler()
{
bool stopDMA = false;
bool hasData = false;
if(stm32_dma_check_ht_flag(AUDIO_DMA, AUDIO_DMA_Stream)) {
stopDMA = audio_update_dma_buffer(0);
if (audio_update_dma_buffer(0)) {
if (_empty_dma_halves < 0xFF) _empty_dma_halves++;
} else {
hasData = true;
}
}

if(stm32_dma_check_tc_flag(AUDIO_DMA, AUDIO_DMA_Stream)) {
stopDMA |= audio_update_dma_buffer(1);
if (audio_update_dma_buffer(1)) {
if (_empty_dma_halves < 0xFF) _empty_dma_halves++;
} else {
hasData = true;
}
}

if (hasData) {
_empty_dma_halves = 0;
}

if(stopDMA) {
if(_empty_dma_halves >= DMA_EMPTY_HALVES_STOP_THRESHOLD) {
_empty_dma_halves = 0;
dac_close_dma_xfer();
}
}
Expand Down