Re: wrong usage of MAX_DMA_ADDRESS in bootmem.h

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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