Messages in this thread | | | Date | Fri, 13 Apr 2007 21:19:04 +0200 (CEST) | From | Guennadi Liakhovetski <> | Subject | dma_declare_coherent_memory() for accessing platform-wide memory |
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Hi
On a PXA270 based system I modified the framebuffer driver to use SRAM on the SoC to reduce bus load caused by DMA transfers. For this I just assigned the entire SRAM to the fb driver. It works.
Then Eric Miao (CCed) rightfully noticed, that other devices might also benefit from using SRAM. So, I started thinking about creating a special (platform) device owning that SRAM block and making all its potential users its children. The device-local memory API even has provisional support for this with the DMA_MEMORY_INCLUDES_CHILDREN flag.
But there are problems with this approach too. For example, some PXA machines already occupy framebuffer's parent. I think, they are fixing power up/down sequence problems in this way, but I am not sure that's a good idea from the point of view of the bus locality.
Otherwise, maybe the best way would be assigning that SRAM block to the struct device platform_bus directly? But that way all platform devices would get their DMA buffers from that (rather small) block on the "first come first served" basis.
What would be the best way to solve this?
Thanks Guennadi --- Guennadi Liakhovetski - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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