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Commit 0718b764 authored by Frode Isaksen's avatar Frode Isaksen Committed by Mark Brown
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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: default avatarFrode Isaksen <fisaksen@baylibre.com>
Signed-off-by: default avatarMark Brown <broonie@kernel.org>
parent 6b3a631e

drivers/spi/spi-davinci.c

+8 −6
Original line number Diff line number Diff line
@@ -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)

	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);



	if (spicfg->io_type != SPI_IO_TYPE_DMA) {

		/* 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);