Messages in this thread Patch in this message | | | From | Nicolin Chen <> | Subject | [RFC/RFT][PATCH v2] dma-mapping: set default segment_boundary_mask to ULONG_MAX | Date | Mon, 6 Apr 2020 14:06:43 -0700 |
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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@gmail.com> --- Changelog: v1->v2 * Followed Robin's comments to revise the commit message by dropping one paragraph of not-entirely-true justification (no git-diff level change, so please ack if you tested v1)
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 330ad58fbf4d..ff8cefe85f30 100644 --- a/include/linux/dma-mapping.h +++ b/include/linux/dma-mapping.h @@ -736,7 +736,7 @@ 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; } static inline int dma_set_seg_boundary(struct device *dev, unsigned long mask) -- 2.17.1
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