From mboxrd@z Thu Jan 1 00:00:00 1970 From: m.szyprowski@samsung.com (Marek Szyprowski) Date: Tue, 13 Jan 2015 12:19:12 +0100 Subject: [PATCH RESEND] dma-mapping: tidy up dma_parms default handling In-Reply-To: References: Message-ID: <54B4FF30.2030607@samsung.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hello, On 2015-01-09 17:56, Robin Murphy wrote: > 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. > > Signed-off-by: Robin Murphy Acked-by: Marek Szyprowski > --- > > Hi, various maintainers from Git logs ;) > > This one's a bit tricky to find a home for - I think technically it's > probably an IOMMU patch, but then the long-underlying problem doesn't > seem to have blown up anything until arm64, and my motivation is to > make bits of Juno work, which seems to nudge it towards arm64/arm-soc > territory. Could anyone suggest which tree is most appropriate? > > Thanks, > Robin. > > 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 c3007cb..99ba736 100644 > --- a/include/linux/dma-mapping.h > +++ b/include/linux/dma-mapping.h > @@ -141,7 +141,9 @@ 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, > @@ -150,14 +152,15 @@ 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) > @@ -165,8 +168,8 @@ 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 Best regards -- Marek Szyprowski, PhD Samsung R&D Institute Poland