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authorTrent Piepho <tpiepho@impinj.com>2019-03-05 02:02:36 +0300
committerMark Brown <broonie@kernel.org>2019-03-11 19:49:16 +0300
commit0a9c8998e75b69b3c347751a65ddd5bf7e72b2dd (patch)
tree6a03c9ef2bf2f024364566f0318848506dddbf5d /drivers/spi/spi-fsl-qspi.c
parenteefffb42f6659c9510105f3e4ebf2a8499d56936 (diff)
downloadlinux-0a9c8998e75b69b3c347751a65ddd5bf7e72b2dd.tar.xz
spi: imx: add module parameter to control DMA use
Add the boolean module parameter "use_dma" to control the use of DMA by the driver. There are about two dozen other drivers with a "use_dma" parameter of some sort. DMA may allow faster and more efficient transfers than using PIO, but it also adds overhead for small transfers. High speed receive operations may be less likely to have issues with FIFO overflow when using DMA than when using PIO. The eCSPI appears to insert a 4 bit pause after each word in DMA mode, not done in PIO mode, which can make DMA transfers 50% slower than PIO. In some cases DMA may be a net win while in others PIO might be. It depends on the application. So allow DMA to be enabled or disabled at the driver level. The default will be to have it enabled when possible. Signed-off-by: Trent Piepho <tpiepho@impinj.com> Signed-off-by: Mark Brown <broonie@kernel.org>
Diffstat (limited to 'drivers/spi/spi-fsl-qspi.c')
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