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SPI transfers larger than what the DMA can handle are split up in multiple transfers.

pull/1132/head
Marcus Chang 2015-05-22 17:30:08 +01:00
parent 88d158e43b
commit f0861ccda5
1 changed files with 32 additions and 1 deletions
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33
libraries/mbed/targets/hal/TARGET_Silicon_Labs/TARGET_EFM32/spi_api.c
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@ -767,8 +767,26 @@ static void spi_activate_dma(spi_t *obj, void* rxdata, void* txdata, int tx_leng
DMA_CfgDescr_TypeDef rxDescrCfg;
DMA_CfgDescr_TypeDef txDescrCfg;
/* Split up transfers if the tx length is larger than what the DMA supports. */
const int DMA_MAX_TRANSFER = (_DMA_CTRL_N_MINUS_1_MASK >> _DMA_CTRL_N_MINUS_1_SHIFT);
if (tx_length > DMA_MAX_TRANSFER)
{
uint32_t max_length = DMA_MAX_TRANSFER;
/* Make sure only an even amount of bytes are transferred
if the width is larger than 8 bits. */
if (obj->spi.bits > 8)
{
max_length = DMA_MAX_TRANSFER - (DMA_MAX_TRANSFER & 0x01);
}
/* Update length for current transfer. */
tx_length = max_length;
}
/* Save amount of TX done by DMA */
obj->tx_buff.pos = tx_length;
obj->tx_buff.pos += tx_length;
if(obj->spi.bits != 9) {
/* Only activate RX DMA if a receive buffer is specified */
@ -966,6 +984,19 @@ uint32_t spi_irq_handler_asynch(spi_t* obj)
if (obj->spi.dmaOptionsTX.dmaUsageState == DMA_USAGE_ALLOCATED || obj->spi.dmaOptionsTX.dmaUsageState == DMA_USAGE_TEMPORARY_ALLOCATED) {
/* DMA implementation */
/* If there is still data in the TX buffer, setup a new transfer. */
if (obj->tx_buff.pos < obj->tx_buff.length)
{
/* Find position and remaining length without modifying tx_buff. */
void* tx_pointer = obj->tx_buff.buffer + obj->tx_buff.pos;
uint32_t tx_length = obj->tx_buff.length - obj->tx_buff.pos;
/* Begin transfer. Rely on spi_activate_dma to split up the transfer further. */
spi_activate_dma(obj, obj->rx_buff.buffer, tx_pointer, tx_length, obj->rx_buff.length);
return 0;
}
/* If there is an RX transfer ongoing, wait for it to finish */
if (DMA_ChannelEnabled(obj->spi.dmaOptionsRX.dmaChannel)) {
/* Check if we need to kick off TX transfer again to force more incoming data. */