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Message-Id: <20200901221646.26491-3-nicoleotsuka@gmail.com>
Date: Tue, 1 Sep 2020 15:16:46 -0700
From: Nicolin Chen <nicoleotsuka@...il.com>
To: hch@....de
Cc: sfr@...b.auug.org.au, mpe@...erman.id.au, benh@...nel.crashing.org,
paulus@...ba.org, linuxppc-dev@...ts.ozlabs.org,
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Subject: [PATCH 2/2] dma-mapping: set default segment_boundary_mask to ULONG_MAX
The default segment_boundary_mask was set to DMA_BIT_MAKS(32)
a decade ago by referencing SCSI/block subsystem, as a 32-bit
mask was good enough for most of the devices.
Now more and more drivers set dma_masks above DMA_BIT_MAKS(32)
while only a handful of them call dma_set_seg_boundary(). This
means that most drivers have a 4GB segmention boundary because
DMA API returns a 32-bit default value, though they might not
really have such a limit.
The default segment_boundary_mask should mean "no limit" since
the device doesn't explicitly set the mask. But a 32-bit mask
certainly limits those devices capable of 32+ bits addressing.
So this patch sets default segment_boundary_mask to ULONG_MAX.
Signed-off-by: Nicolin Chen <nicoleotsuka@...il.com>
---
include/linux/dma-mapping.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index faab0a8210b9..df0bff2ea750 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -629,7 +629,7 @@ static inline unsigned long dma_get_seg_boundary(struct device *dev)
{
if (dev->dma_parms && dev->dma_parms->segment_boundary_mask)
return dev->dma_parms->segment_boundary_mask;
- return DMA_BIT_MASK(32);
+ return ULONG_MAX;
}
/**
--
2.17.1
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