[PATCH 08/10 RESEND] spi: Add DMA support into SPI driver
marex at denx.de
Thu Aug 2 11:00:42 EDT 2012
Dear Mark Brown,
> On Mon, Jul 23, 2012 at 10:40:50PM +0200, Marek Vasut wrote:
> > + /*
> > + * Small blocks can be transfered via PIO.
> > + * Measured by empiric means:
> > + *
> > + * dd if=/dev/mtdblock0 of=/dev/null bs=1024k count=1
> > + *
> > + * DMA only: 2.164808 seconds, 473.0KB/s
> > + * Combined: 1.676276 seconds, 610.9KB/s
> > + */
> I've seen other devices end up using the FIFO length as the decision
> point here which makes intuitive sense to me unless the FIFO is
> extremely deep.
Yep, that's all good. This device has not too deep FIFO, but the reason I chose
not to go that way is because the DMA allocations have some overhead too and
this values seemed to be the best.
> Not reviewed this properly yet but it looks OK from a first read
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