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stm32: performance improvement for spi on stm32f0 

The stm32 has a small queue for spi tx/rx. The current code only uses the
spi with a single byte buffer, effectively waiting for each byte to complete
before starting the next transfer.
This patch changes the structure of spi_transfer() to make use of the queue
and achieve back-to-back transfer of bytes on spi.

Signed-off-by: Arne Jansen <arne@die-jansens.de>
This commit is contained in:
Arne Jansen 2020-01-19 08:42:20 +00:00 committed by KevinOConnor
parent ce35ee45d6
commit a2c309a2b0
1 changed files with 8 additions and 4 deletions
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12
src/stm32/spi.c
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@ -84,10 +84,14 @@ spi_transfer(struct spi_config config, uint8_t receive_data,
uint8_t len, uint8_t *data) uint8_t len, uint8_t *data)
{ {
SPI_TypeDef *spi = config.spi; SPI_TypeDef *spi = config.spi;
while (len--) { uint8_t *wptr = data;
writeb((void *)&spi->DR, *data); uint8_t *end = data + len;
while (!(spi->SR & SPI_SR_RXNE))
; while (data < end) {
if (spi->SR & SPI_SR_TXE && wptr < end)
writeb((void *)&spi->DR, *wptr++);
if (!(spi->SR & SPI_SR_RXNE))
continue;
uint8_t rdata = readb((void *)&spi->DR); uint8_t rdata = readb((void *)&spi->DR);
if (receive_data) if (receive_data)
*data = rdata; *data = rdata;