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Minimum DMA bytes required for transfer

rahul r
Intellectual 420 points


Hi ,

I am working on 3.12 kernel . In file /drivers/spi/spi-omap2-mcspi.c lin2 - Line no 120 says 

#define DMA_MIN_BYTES  160

Why is it only 160 ? why not 120 or any other number ?

Thanks

rahul

  • 0
    Expert 1185 points
    Hi Rahul,

    DMA_MIN_BYTES is the threshold for McSPI driver switching from PIO mode to DMA.
    It is defined, taking into account maximum throughput of PIO mode and minimum throughput of DMA mode.
    Why exactly 160, may be the better idea is to ask driver authors.

    BR,
    Georgi