Messages in this thread | | | Date | Wed, 18 May 2016 14:45:55 +0100 | From | Catalin Marinas <> | Subject | Re: [PATCH] arm64: Allow for different DMA and CPU bus offsets |
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On Wed, May 18, 2016 at 12:52:28PM +0200, Arnd Bergmann wrote: > On Wednesday 18 May 2016 11:33:01 Alexander Graf wrote: > > diff --git a/arch/arm64/include/asm/dma-mapping.h b/arch/arm64/include/asm/dma-mapping.h > > index ba437f0..67bf8e1 100644 > > --- a/arch/arm64/include/asm/dma-mapping.h > > +++ b/arch/arm64/include/asm/dma-mapping.h > > @@ -66,12 +66,16 @@ static inline bool is_device_dma_coherent(struct device *dev) > > > > static inline dma_addr_t phys_to_dma(struct device *dev, phys_addr_t paddr) > > { > > - return (dma_addr_t)paddr; > > + dma_addr_t dev_addr = (dma_addr_t)paddr; > > + > > + return dev_addr - (dma_addr_t)__pfn_to_phys(dev->dma_pfn_offset); > > } > > > > static inline phys_addr_t dma_to_phys(struct device *dev, dma_addr_t dev_addr) > > { > > - return (phys_addr_t)dev_addr; > > + phys_addr_t paddr = (phys_addr_t)dev_addr; > > + > > + return paddr + __pfn_to_phys(dev->dma_pfn_offset); > > } > > > > The patch looks ok overall, but I think it's better to use an open-coded > shift instead of __pfn_to_phys/__pfn_to_phys here: those helpers convert > between actual page frame numbers and addresses, which may not always > be a 1:1 relationship, e.g. if someone wants to work around the crazy > "Principles of ARM Memory Maps White Paper" layout.
Nitpick: Even better to use the PFN_PHYS() macro as it matches the PFN_DOWN() in of_dma_configure(). I can fix it up when applying.
-- Catalin
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