On Tue, 31 Jul 2018 11:29:24 +0800 Jisheng Zhang <Jisheng.Zhang@xxxxxxxxxxxxx> wrote: > Hi Robin, > > On Mon, 30 Jul 2018 12:06:08 +0100 Robin Murphy wrote: > > > Hi Jisheng, > > > > On 26/07/18 08:14, Jisheng Zhang wrote: > > > When using DMA, if the DMA addr spans 128MB boundary, we have to split > > > the DMA transfer into two so that each one doesn't exceed the boundary. > > > > Out of interest, is the driver already setting its segment boundary mask > > appropriately? This sounds like the exact kind of hardware restriction > > that dma_parms is intended to describe, which scatterlist-generating > > code is *supposed* to already respect. > > Thanks for the nice input. It may provide an elegant solution for this > limitation. > > To simplify the situation, let's assume no iommu, only swiotlb. And > the DDR is less than 4GB so swiotlb on arm64 doesn't init. > > There's no dma range limitation with the HW, the only limitation > is boundary, while dma_capable() doesn't check the boundary mask, so if > we taking this solution, we need to teach dma_capable() about the boundary > mask, I'm not sure whether this is acceptable. > > Another problem is swiotlb initialization. When to init swiotlb, we dunno > there's such boundary limitation HW. Is there any elegant solution for > this problem? > One more problem is: swiotlb isn't available on all platforms, e.g arm? How to solve this SDHCI HW's limitation on arm soc w/o iommu? Thanks -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
