Messages in this thread |  | | Subject | Re: DMA memory limitation? | Date | Thu, 5 Jul 2001 12:53:45 +0100 (BST) | From | Alan Cox <> |
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> Is there any limitation on DMA memory we can allocate using > kmalloc(size, GFP_DMA)? I am not able to acquire more than > 14MB of the mem using this on my PCI SMP box with 256MB ram. > I think there is restriction on ISA boards of 16MB.
Yes. GFP_DMA allocates memory below 16Mbytes for ISA devices and that is a physical wiring issue. For PCI devices you can allocate a lot more using the pci_alloc_* and pci_map_* interface to allocate memory for PCI in a CPU independant manner. It'll also then look after cache coherency issues for you
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