[PATCH 28/33] dma-direct: add support for allocation from ZONE_DMA and ZONE_DMA32
From: hch@lst.de (Christoph Hellwig)
Date: 2018-01-10 08:04:05
Also in:
linux-alpha, linux-arch, linux-iommu, linux-mips, linux-s390, linux-sh, linuxppc-dev, lkml, sparclinux
Subsystem:
library code, the rest · Maintainers:
Andrew Morton, Linus Torvalds
This allows to dip into zones for lower memory if they are available. If one of the zones is not available the corresponding GFP_* flag will evaluate to 0 so they won't change anything. We provide an arch tunable for those architectures that do not use GFP_DMA for the lowest 24-bits, given that there are a few. Roughly based on the x86 code. Signed-off-by: Christoph Hellwig <hch@lst.de> --- lib/dma-direct.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+)
diff --git a/lib/dma-direct.c b/lib/dma-direct.c
index f04a424f91fa..8f76032ebc3c 100644
--- a/lib/dma-direct.c
+++ b/lib/dma-direct.c@@ -12,6 +12,14 @@ #define DIRECT_MAPPING_ERROR 0 +/* + * Most architectures use ZONE_DMA for the first 16 Megabytes, but + * some use it for entirely different regions: + */ +#ifndef ARCH_ZONE_DMA_BITS +#define ARCH_ZONE_DMA_BITS 24 +#endif + static bool check_addr(struct device *dev, dma_addr_t dma_addr, size_t size, const char *caller)
@@ -34,6 +42,12 @@ static void *dma_direct_alloc(struct device *dev, size_t size, int page_order = get_order(size); struct page *page = NULL; + /* GFP_DMA32 and GFP_DMA are no ops without the corresponding zones: */ + if (dev->coherent_dma_mask <= DMA_BIT_MASK(ARCH_ZONE_DMA_BITS)) + gfp |= GFP_DMA; + if (dev->coherent_dma_mask <= DMA_BIT_MASK(32) && !(gfp & GFP_DMA)) + gfp |= GFP_DMA32; + /* CMA can be used only in the context which permits sleeping */ if (gfpflags_allow_blocking(gfp)) page = dma_alloc_from_contiguous(dev, count, page_order, gfp);
--
2.14.2