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. Regards 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/
