Re: PowerPC PCI DMA issues (prefetch/coherency?)

From: Chris Pringle
Date: Wed Jun 17 2009 - 03:58:32 EST


I've just tried this (I had to edit Kconfig in power/platforms to make the build system accept it), and interestingly it's making no difference. I'm using streaming mappings, and are using the pci_map_sg functions to ensure the memory is mapped/flushed correctly. I've also explicitly put in a pci_dma_sync_sg_for_device, however that's also not made any difference. Turning the cpu cache snoop off has the same affect as it did without CONFIG_NOT_COHERENT_CACHE; it gets much worse. Any other ideas?

Will back off the low latency patches next, and give 2.6.30 a try - see if that makes any difference.


Chris Pringle
Software Engineer

Miranda Technologies Ltd.
Hithercroft Road
Oxfordshire OX10 9DG

Tel. +44 1491 820206
Fax. +44 1491 820001


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