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dma-mapping: tidy up dma_parms default handling 

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.

[akpm@linux-foundation.org: dma-mapping.h needs sizes.h for SZ_64K]
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Reviewed-by: Sumit Semwal <sumit.semwal@linaro.org>
Acked-by: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Sakari Ailus <sakari.ailus@iki.fi>
Cc: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
hifive-unleashed-5.1
Robin Murphy 2015-11-06 16:32:51 -08:00 committed by Linus Torvalds
parent 8639b46139
commit 002edb6f6f
1 changed files with 11 additions and 7 deletions
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18
include/linux/dma-mapping.h
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@ -1,6 +1,7 @@
#ifndef _LINUX_DMA_MAPPING_H
#define _LINUX_DMA_MAPPING_H
#include <linux/sizes.h>
#include <linux/string.h>
#include <linux/device.h>
#include <linux/err.h>
@ -145,7 +146,9 @@ 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 +157,15 @@ 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 +173,8 @@ 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