Jivin Markus Franke lays it down ... > Dear uClinux Developers, > > I am not sure if this is already offtopic here. > As per my knowledge the ZONE_DMA memory zone is a 16-Mbyte's memory > area within 0x0 - 0x00ffffff which should be used for any allocation > which needs to be used in DMA transfers. This zone actually is a > result of legacy ISA devices which can do DMA transfers only from the > lower 16 Mbyte's of memory. > > I wonder whether it might be possible to shift this memory zone to > some different location, like at the end of memory? I know that the > size of the zone can be modified via linux/arch/<myarch>/mm/init.c and > the zones array. But how about the positioning of this zone? > I know that something like this was done in the blackfin architecture > which is only present in the standard linux tree. But they handle all > memory allocations by their own simple memory allocator which doesn't > look really performant. (see arch/blackfin/kernel/dma-mapping.c @ > function __alloc_dma_pages for reference) > > Concretely spoken I am dealing with m68knommu/coldfire architecture. I > want to move the DMA zone to a different location because Coldfire > MCF548x, respectively its cache doesn't support bus snooping. So I > simply want to reserve a zone of, let's say, 8 MByte at the end of my > main memory for all DMA allocations. Once this is done I want to > exclude this memory area from caching mechanisms.ยด > > Another solution: > Would it be better to move the linux kernel to a different location in > memory (e.g. @ 0x01000000) and keep the ZONE_DMA zone @ 0x0 - > 0x00ffffff?
My understanding of the zones says is that you can do what you are trying to do. I seem to recall that if you get low on normal memory the system may dip into the DMA pool. Cheers, Davidm -- David McCullough, [EMAIL PROTECTED], Ph:+61 734352815 Secure Computing - SnapGear http://www.uCdot.org http://www.cyberguard.com _______________________________________________ uClinux-dev mailing list [email protected] http://mailman.uclinux.org/mailman/listinfo/uclinux-dev This message was resent by [email protected] To unsubscribe see: http://mailman.uclinux.org/mailman/options/uclinux-dev
