From mboxrd@z Thu Jan 1 00:00:00 1970 From: Robin Murphy Subject: [PATCH RESEND] dma-mapping: tidy up dma_parms default handling Date: Fri, 9 Jan 2015 16:56:03 +0000 Message-ID: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: will.deacon-5wv7dgnIgG8@public.gmane.org, arnd-r2nGTMty4D4@public.gmane.org, m.szyprowski-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org, bhelgaas-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org, joro-zLv9SwRftAIdnm+yROfE0A@public.gmane.org, gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org Cc: iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org List-Id: iommu@lists.linux-foundation.org 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 --- 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 -- 1.9.1