[PATCH v3 4/6] spi: davinci: do not use DMA if transfer length is less than 16
From: Frode Isaksen <hidden>
Date: 2017-02-23 18:01:59
Also in:
linux-spi
Subsystem:
spi subsystem, the rest · Maintainers:
Mark Brown, Linus Torvalds
Higher bitrate and lower CPU load if using PIO in this case. Signed-off-by: Frode Isaksen <redacted> --- drivers/spi/spi-davinci.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-)
diff --git a/drivers/spi/spi-davinci.c b/drivers/spi/spi-davinci.c
index ca12216..75c658e 100644
--- a/drivers/spi/spi-davinci.c
+++ b/drivers/spi/spi-davinci.c@@ -109,6 +109,8 @@ #define SPIDEF 0x4c #define SPIFMT0 0x50 +#define DMA_MIN_BYTES 16 + /* SPI Controller driver's private data. */ struct davinci_spi { struct spi_bitbang bitbang;
@@ -479,7 +481,8 @@ static bool davinci_spi_can_dma(struct spi_master *master, bool can_dma = false; if (spicfg) - can_dma = spicfg->io_type == SPI_IO_TYPE_DMA; + can_dma = (spicfg->io_type == SPI_IO_TYPE_DMA) && + (xfer->len >= DMA_MIN_BYTES); return can_dma; }
@@ -620,10 +623,9 @@ static int davinci_spi_bufs(struct spi_device *spi, struct spi_transfer *t) reinit_completion(&dspi->done); - if (spicfg->io_type == SPI_IO_TYPE_INTR) - set_io_bits(dspi->base + SPIINT, SPIINT_MASKINT); - - if (spicfg->io_type != SPI_IO_TYPE_DMA) { + if (!davinci_spi_can_dma(spi->master, spi, t)) { + if (spicfg->io_type != SPI_IO_TYPE_POLL) + set_io_bits(dspi->base + SPIINT, SPIINT_MASKINT); /* start the transfer */ dspi->wcount--; tx_data = dspi->get_tx(dspi);
@@ -698,7 +700,7 @@ static int davinci_spi_bufs(struct spi_device *spi, struct spi_transfer *t) } clear_io_bits(dspi->base + SPIINT, SPIINT_MASKALL); - if (spicfg->io_type == SPI_IO_TYPE_DMA) + if (davinci_spi_can_dma(spi->master, spi, t)) clear_io_bits(dspi->base + SPIINT, SPIINT_DMA_REQ_EN); clear_io_bits(dspi->base + SPIGCR1, SPIGCR1_SPIENA_MASK);
--
2.7.4