[PATCH 2/4] dma-mapping: Tidy up dma_parms default handling
From: robin.murphy@arm.com (Robin Murphy)
Date: 2015-09-25 12:17:16
Also in:
linux-arch, linux-mm, lkml
Subsystem:
dma mapping helpers, the rest · Maintainers:
Marek Szyprowski, Linus Torvalds
Many DMA controllers and other devices set max_segment_size to indicate their scatter-gather capability, but have no interest in segment_boundary_mask. However, the existence of a dma_parms structure precludes the use of any default value, leaving them as zeros (assuming a properly kzalloc'ed structure). If a well-behaved IOMMU (or SWIOTLB) then tries to respect this by ensuring a mapped segment does not cross a zero-byte boundary, hilarity ensues. Since zero is a nonsensical value for either parameter, treat it as an indicator for "default", as might be expected. In the process, clean up a bit by replacing the bare constants with slightly more meaningful macros and removing the superfluous "else" statements. Acked-by: Marek Szyprowski <m.szyprowski@samsung.com> Reviewed-by: Sumit Semwal <sumit.semwal@linaro.org> Signed-off-by: Robin Murphy <robin.murphy@arm.com> --- include/linux/dma-mapping.h | 17 ++++++++++------- 1 file changed, 10 insertions(+), 7 deletions(-)
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index ac07ff0..ac9af22 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h@@ -145,7 +145,9 @@ static inline void arch_teardown_dma_ops(struct device *dev) { } static inline unsigned int dma_get_max_seg_size(struct device *dev) { - return dev->dma_parms ? dev->dma_parms->max_segment_size : 65536; + if (dev->dma_parms && dev->dma_parms->max_segment_size) + return dev->dma_parms->max_segment_size; + return SZ_64K; } static inline unsigned int dma_set_max_seg_size(struct device *dev,
@@ -154,14 +156,15 @@ static inline unsigned int dma_set_max_seg_size(struct device *dev, if (dev->dma_parms) { dev->dma_parms->max_segment_size = size; return 0; - } else - return -EIO; + } + return -EIO; } static inline unsigned long dma_get_seg_boundary(struct device *dev) { - return dev->dma_parms ? - dev->dma_parms->segment_boundary_mask : 0xffffffff; + if (dev->dma_parms && dev->dma_parms->segment_boundary_mask) + return dev->dma_parms->segment_boundary_mask; + return DMA_BIT_MASK(32); } static inline int dma_set_seg_boundary(struct device *dev, unsigned long mask)
@@ -169,8 +172,8 @@ static inline int dma_set_seg_boundary(struct device *dev, unsigned long mask) if (dev->dma_parms) { dev->dma_parms->segment_boundary_mask = mask; return 0; - } else - return -EIO; + } + return -EIO; } #ifndef dma_max_pfn
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1.9.1