From mboxrd@z Thu Jan 1 00:00:00 1970 From: fisaksen@baylibre.com (Frode Isaksen) Date: Thu, 23 Feb 2017 19:01:59 +0100 Subject: [PATCH v3 4/6] spi: davinci: do not use DMA if transfer length is less than 16 In-Reply-To: <1487872921-26628-1-git-send-email-fisaksen@baylibre.com> References: <1487872921-26628-1-git-send-email-fisaksen@baylibre.com> Message-ID: <1487872921-26628-5-git-send-email-fisaksen@baylibre.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Higher bitrate and lower CPU load if using PIO in this case. Signed-off-by: Frode Isaksen --- 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