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* [PATCH/RFC 0/2] SPI: DMA support for MSIOF
@ 2011-01-24 10:24 Guennadi Liakhovetski
  2011-01-24 10:24 ` [PATCH/RFC 1/2] SPI: spi_sh_msiof: implement DMA support Guennadi Liakhovetski
  2011-01-24 10:24 ` [PATCH/RFC 2/2] sh: use DMA with MSIOF SPI on the sh7724 ecovec board Guennadi Liakhovetski
  0 siblings, 2 replies; 3+ messages in thread
From: Guennadi Liakhovetski @ 2011-01-24 10:24 UTC (permalink / raw)
  To: spi-devel-general; +Cc: linux-sh

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

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2011-01-24 10:24 [PATCH/RFC 0/2] SPI: DMA support for MSIOF Guennadi Liakhovetski
2011-01-24 10:24 ` [PATCH/RFC 1/2] SPI: spi_sh_msiof: implement DMA support Guennadi Liakhovetski
2011-01-24 10:24 ` [PATCH/RFC 2/2] sh: use DMA with MSIOF SPI on the sh7724 ecovec board Guennadi Liakhovetski

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