On Wed, Feb 19, 2014 at 02:32:28PM +0100, Geert Uytterhoeven wrote: > On Wed, Feb 19, 2014 at 2:04 PM, Mark Brown <broonie@xxxxxxxxxx> wrote: > > This is a particularly thoughtless hardware design it has to be said. > Do you mean the fact that you need to transmit dummy data on this particular > hardware, or that you need to know the direction for Dual/Quad transfers, > and don't need dummy data for the latter? The combination of the two, clearly the hardware can actually cope with an empty transmit FIFO. > > That's readily fixable for DMA capable drivers, we can just repeatedly > > transfer the same page (or whatever). PIO drivers have big problems > So let's hope all DMA-capable hardware has scatter/gather support, or an > IOMMU ;-) You can emulate scatter/gather well enough for most SPI controllers anyway.
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