Messages in this thread | | | From | Arnd Bergmann <> | Subject | Re: For the problem when using swiotlb | Date | Mon, 17 Nov 2014 13:18:42 +0100 |
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On Monday 17 November 2014 19:56:27 Ding Tianhong wrote: > Hi Catalin: > 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.
Arnd
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