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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: Frode Isaksen <fisaksen@baylibre.com> Signed-off-by: Mark Brown <broonie@kernel.org>
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6b3a631e7f
commit
0718b76488
1 changed files with 8 additions and 6 deletions
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@ -109,6 +109,8 @@
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#define SPIDEF 0x4c
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#define SPIFMT0 0x50
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#define DMA_MIN_BYTES 16
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/* SPI Controller driver's private data. */
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struct davinci_spi {
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struct spi_bitbang bitbang;
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@ -479,7 +481,8 @@ static bool davinci_spi_can_dma(struct spi_master *master,
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bool can_dma = false;
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if (spicfg)
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can_dma = spicfg->io_type == SPI_IO_TYPE_DMA;
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can_dma = (spicfg->io_type == SPI_IO_TYPE_DMA) &&
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(xfer->len >= DMA_MIN_BYTES);
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return can_dma;
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}
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@ -620,10 +623,9 @@ static int davinci_spi_bufs(struct spi_device *spi, struct spi_transfer *t)
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reinit_completion(&dspi->done);
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if (spicfg->io_type == SPI_IO_TYPE_INTR)
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set_io_bits(dspi->base + SPIINT, SPIINT_MASKINT);
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if (spicfg->io_type != SPI_IO_TYPE_DMA) {
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if (!davinci_spi_can_dma(spi->master, spi, t)) {
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if (spicfg->io_type != SPI_IO_TYPE_POLL)
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set_io_bits(dspi->base + SPIINT, SPIINT_MASKINT);
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/* start the transfer */
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dspi->wcount--;
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tx_data = dspi->get_tx(dspi);
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@ -698,7 +700,7 @@ static int davinci_spi_bufs(struct spi_device *spi, struct spi_transfer *t)
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}
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clear_io_bits(dspi->base + SPIINT, SPIINT_MASKALL);
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if (spicfg->io_type == SPI_IO_TYPE_DMA)
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if (davinci_spi_can_dma(spi->master, spi, t))
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clear_io_bits(dspi->base + SPIINT, SPIINT_DMA_REQ_EN);
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clear_io_bits(dspi->base + SPIGCR1, SPIGCR1_SPIENA_MASK);
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