Messages in this thread | | | From | Guennadi Liakhovetski <> | Subject | [PATCH/RFC 0/4] dmaengine: add DT support for DMA multiplexers | Date | Tue, 30 Apr 2013 09:11:19 +0200 |
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Previously an issue has been discussed, arising on sh-/r-mobile ARM-based systems. There we typically have multiple DMA controller instances with exactly equal or very similar capabilities. Each of them can serve the same slaves, using the same slave identifiers (request line IDs). With the present DMA DT implementation _each_ such DMA slave would have to reference _each_ of those DMA controllers in its DMA bindings, e.g.
mmc0: mmc@10000000 { ... dmas = <&dma0 0x10 &dma1 0x10 &dma2 0x10 &dma3 0x10 &dma0 0x11 &dma1 0x11 &dma2 0x11 &dma3 0x11>; dma-names = "tx", "tx", "tx", "tx", "rx", "rx", "rx", "rx"; };
Which certainly isn't pretty. To avoid such redundancy it has been proposed to implement a DMA multiplexer DT node. That way slaves would just reference the multiplexer and one of DMA controller instances in it would be picked up automatically to provide DMA channels to slaves. Patches 1-3 in this series propose such an implementation. Patch 4 is just a minor clean up, can be applied independently.
Cc: Guennadi Liakhovetski <g.liakhovetski+renesas@gmail.com>
Guennadi Liakhovetski (4): OF: add a new phandle parsing function for grouped nodes dmaengine: add support for DMA multiplexer DT nodes ARM: shmobile: move r8a7740 DMA controller DT node under a "dma-mux" node OF: modify function stubs to match proper function declarations.
Documentation/devicetree/bindings/dma/dma.txt | 44 ++++++++++++++++++++ .../boot/dts/r8a7740-armadillo800eva-reference.dts | 12 +++--- arch/arm/boot/dts/r8a7740.dtsi | 43 +++++++++++-------- drivers/dma/of-dma.c | 39 +++++++++++++---- drivers/of/base.c | 28 +++++++++++- include/linux/of.h | 20 ++++++++- 6 files changed, 147 insertions(+), 39 deletions(-)
-- 1.7.2.5
Thanks Guennadi --- Guennadi Liakhovetski, Ph.D. Freelance Open-Source Software Developer http://www.open-technology.de/
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