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x86: use GFP_DMA for 24bit coherent_dma_mask 

dma_alloc_coherent (include/asm-x86/dma-mapping.h) avoids GFP_DMA
allocation first and if the allocated address is not fit for the
device's coherent_dma_mask, then dma_alloc_coherent does GFP_DMA
allocation. This is because dma_alloc_coherent avoids precious GFP_DMA
zone if possible. This is also how the old dma_alloc_coherent
(arch/x86/kernel/pci-dma.c) works.

However, if the coherent_dma_mask of a device is 24bit, there is no
point to go into the above GFP_DMA retry mechanism. We had better use
GFP_DMA in the first place.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Tested-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
FUJITA Tomonori 2008-10-23 20:46:55 +09:00 committed by Ingo Molnar
parent a2b89b596c
commit 75bebb7f0c
1 changed files with 3 additions and 1 deletions
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4
arch/x86/include/asm/dma-mapping.h
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@ -255,9 +255,11 @@ static inline unsigned long dma_alloc_coherent_mask(struct device *dev,
static inline gfp_t dma_alloc_coherent_gfp_flags(struct device *dev, gfp_t gfp)
{
#ifdef CONFIG_X86_64
unsigned long dma_mask = dma_alloc_coherent_mask(dev, gfp);
if (dma_mask <= DMA_24BIT_MASK)
gfp |= GFP_DMA;
#ifdef CONFIG_X86_64
if (dma_mask <= DMA_32BIT_MASK && !(gfp & GFP_DMA))
gfp |= GFP_DMA32;
#endif