[PATCH/RFC 0/2] SPI: DMA support for MSIOF

The MSIOF controller on sh-mobile systems can use DMA for data transfers. 
This patch implements support for it, using the sh_dma dmaengine driver. 
Attention: this is only RFC / for information now, because DMA mode is 
unstable in my stress-tests. So far only tested on ecovec with an SD-card, 
which works stably in PIO mode. Still, it is possible, that this is an 
electric problem and DMA just changes the bus-usage pattern. DMA on MSIOF 
also suffers from the maximum transfer length limit of 256 words. In 8-bit 
mode, which is also used for mmc_spi, with the recent 32-bit consolidation 
we also transmit 256 bytes per transfer, so, in this mode we don't benefit 
from DMA.

Thanks
Guennadi
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Guennadi Liakhovetski, Ph.D.
Freelance Open-Source Software Developer
http://www.open-technology.de/