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authorFrode Isaksen <fisaksen@baylibre.com>2017-02-23 21:01:59 +0300
committerMark Brown <broonie@kernel.org>2017-03-15 22:35:39 +0300
commit0718b764880434ac7a5b7c0f5cb2c805c589a807 (patch)
tree8e173273f8ca2d1e856061716c6da501b38c17b5 /drivers
parent6b3a631e7f8eca75a987ed760898d28fb3628143 (diff)
downloadlinux-0718b764880434ac7a5b7c0f5cb2c805c589a807.tar.xz
spi: davinci: do not use DMA if transfer length is less than 16
Higher bitrate and lower CPU load if using PIO in this case. Signed-off-by: Frode Isaksen <fisaksen@baylibre.com> Signed-off-by: Mark Brown <broonie@kernel.org>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/spi/spi-davinci.c14
1 files changed, 8 insertions, 6 deletions
diff --git a/drivers/spi/spi-davinci.c b/drivers/spi/spi-davinci.c
index ca122165a3c6..75c658e4e487 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);