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Date: Fri, 21 Nov 2014 13:48:09 +0100 From: Arnd Bergmann <arnd@...db.de> To: linux-arm-kernel@...ts.infradead.org Cc: Catalin Marinas <catalin.marinas@....com>, Will Deacon <Will.Deacon@....com>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Ding Tianhong <dingtianhong@...wei.com> Subject: Re: For the problem when using swiotlb On Friday 21 November 2014 09:35:10 Catalin Marinas wrote: > On Thu, Nov 20, 2014 at 07:40:00AM +0000, Arnd Bergmann wrote: > > On Thursday 20 November 2014 10:57:53 Ding Tianhong wrote: > > But this wouldn't help Ding's case, here the driver needs to set the > wider DMA mask. > > Anyway, back to your point, to make sure I understand what you meant (I > can send a proper patch with log afterwards): Thanks for putting this into code! > @@ -88,11 +89,24 @@ static inline int dma_set_mask(struct device *dev, u64 mask) > { > if (!dev->dma_mask || !dma_supported(dev, mask)) > return -EIO; > + /* if asking for bigger dma mask, limit it to the bus dma ranges */ > + if (mask > *dev->dma_mask) > + mask &= of_dma_get_range_mask(dev); > *dev->dma_mask = mask; > > return 0; > } As you commented later, the dma_supported check indeed needs to happen after the masking. > +static inline int dma_set_coherent_mask(struct device *dev, u64 mask) > +{ > + if (!dma_supported(dev, mask)) > + return -EIO; > + if (mask > dev->coherent_dma_mask) > + mask &= of_dma_get_range_mask(dev); > + dev->coherent_dma_mask = mask; > + return 0; > +} There is an interesting side problem here: the dma mask points to coherent_dma_mask for all devices probed from DT, so this breaks if we have any driver that sets them to different values. It is a preexisting problem them. > EXPORT_SYMBOL_GPL(of_dma_get_range); > > +u64 of_dma_get_range_mask(struct device *dev) > +{ > + u64 dma_addr, paddr, size; > + > + /* no dma mask limiting if no of_node or no dma-ranges property */ > + if (!dev->of_node || > + of_dma_get_range(dev->of_node, &dma_addr, &paddr, &size) < 0) > + return DMA_BIT_MASK(64); If no dma-ranges are present, we should assume that the bus only supports 32-bit DMA, or we could make it architecture specific. It would probably be best for arm64 to require a dma-ranges property for doing any DMA at all, but we can't do that on arm32 any more now. > diff --git a/drivers/of/platform.c b/drivers/of/platform.c > index 3b64d0bf5bba..50d1ac4739e6 100644 > --- a/drivers/of/platform.c > +++ b/drivers/of/platform.c > @@ -200,6 +200,10 @@ static void of_dma_configure(struct device *dev) > /* DMA ranges found. Calculate and set dma_pfn_offset */ > dev->dma_pfn_offset = PFN_DOWN(paddr - dma_addr); > dev_dbg(dev, "dma_pfn_offset(%#08lx)\n", dev->dma_pfn_offset); > + > + /* limit the coherent_dma_mask to the dma-ranges size property */ I would change the comment to clarify that we are actually changing the dma_mask here as well. > + if (size < (1ULL << 32)) > + dev->coherent_dma_mask = DMA_BIT_MASK(ilog2(size)); > } > As you mentioned in another mail in this thread, we wouldn't be able to suuport this case on arm64. Arnd -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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