Messages in this thread | | | Date | Tue, 30 Sep 2008 14:56:26 -0500 | From | Christoph Lameter <> | Subject | Re: wrong usage of MAX_DMA_ADDRESS in bootmem.h |
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Nicolas Pitre wrote: > I have implemented highmem for ARM. To catch wrong usage of __pa() and > > One issue is that bootmem.h uses __pa(MAX_DMA_ADDRESS). However > MAX_DMA_ADDRESS on ARM is defined as 0xffffffff because there is usually > no restriction on the maximum DMA-able address. > > RMK suggested that those places should be using ISA_DMA_THRESHOLD > instead -- here's an excert of our conversation on this topic: >
ok so do
#define MAX_DMA_ADDRESS ISA_DMA_THRESHOLD
>> I suspect all those places which are doing __pa(MAX_DMA_ADDRESS) really >> want to be using ISA_DMA_THRESHOLD - that's something to raise on LKML >> if it's causing problems.
MAX_DMA_ADDRESS is the highest address used for ZONE_DMA / GFP_DMA
Does ISA_DMA_THRESHOLD have any meaning on ARM? If you use old ISA stuff then you need CONFIG_ZONE_DMA and therefore also MAX_DMA_ADDRESS.
If not then there is no need to define CONFIG_ZONE_DMA and MAX_DMA_ADDRESS looses its usual meaning.
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