On 2014/11/19 16:45, Arnd Bergmann wrote: > On Wednesday 19 November 2014 11:17:15 Ding Tianhong wrote: >> On 2014/11/18 2:09, Catalin Marinas wrote: >>> On Mon, Nov 17, 2014 at 12:18:42PM +0000, Arnd Bergmann wrote: >>>> On Monday 17 November 2014 19:56:27 Ding Tianhong wrote: >>>>> The commit 3690951fc6d42f3a0903987677d0e592c49dd8db(arm64: Use >>>>> swiotlb late initialisation) >>>>> switches the DMA mapping code to >>>>> swiotlb_tlb_late_init_with_default_size(), this will occur a problem >>>>> when I run the scsi stress tests, the message as below: >>>>> >>>>> sas_controller b1000000.sas: swiotlb buffer is full (sz: 65536 >>>>> bytes).. >>>>> DMA: Out of SW-IOMMU space for 65536 bytes at device b1000000.sas >>>>> >>>>> The reason is that the swiotlb_tlb_late_init_with_default_size() could >>>>> only alloc 16M memory for DMA-mapping, >>>>> and the param in cmdline "swiotlb=xxx" is useless because the >>>>> get_free_pages() only use the buddy to assigned a >>>>> maximum memory of 16M(The MAX_ORDER is 13 for 4k pages), obviously 16M is >>>>> too small in many scenes, but >>>>> the swiotlb_init() which could reserved a bigger memory as wished could >>>>> work well for most drivers. >>>>> >>>>> I could not get a better way to fix this problem except to revert this >>>>> patch, so could you please give me some >>>>> advise and help me, thanks very much. >>>> >>>> In general, you should not need to use swiotlb for most devices, in >>>> particular for high-performance devices like network or block. >>>> >>>> Please make sure that you have set up the dma-ranges properties in >>>> your DT properly to allow 64-bit DMA if the device supports it. >>> >>> That's the problem indeed, the DMA API ends up using swiotlb bounce >>> buffers because the physical address of the pages passed to (or >>> allocated by) the driver are beyond 32-bit limit (which is the default >>> dma mask). >>> >> >> Thanks everyone, I think I found the way to fix it, need to enable DMA_CMA, >> to reserve a big memory >> for CMA and set coherent mask for dev, then dma_alloc and dma_mapping will >> not use the swiotlb until >> the memory out of mask or swiotlb_force is enabled. >> >> If I still understand uncorrectly, please inform me. >> > > Please do not use CMA to work around the problem, but fix the underlying bug > instead. > > The driver should call 'dma_set_mask_and_coherent()' with the appropriate > dma mask, and check whether that succeeded. However, the code implementing > dma_set_mask_and_coherent on arm64 also needs to be changed to look up > the dma-ranges property (see of_dma_configure()), and check if the mask > is possible. > > Arnd >
The dma_pfn_offset looks only support arm32, but my platform is aarch64 and I check the latest kernel version, I think the dma-rangs still could not work for aarch64, so maybe we should add dma_pfn_offset for aarch64 first. Ding > . > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/