Hi Tom,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on rockchip/for-next]
[cannot apply to iommu/next tegra/for-next vfio/next linus/master v5.5-rc3 next-20191219]
[if your patch is applied to the wrong git tree, please drop us a note to help
improve the system. BTW, we also suggest to use '--base' option to specify the
base tree in git format-patch, please see https://stackoverflow.com/a/37406982]

url:    https://github.com/0day-ci/linux/commits/Tom-Murphy/Convert-the-intel-iommu-driver-to-the-dma-iommu-api/20191224-171249
base:   https://git.kernel.org/pub/scm/linux/kernel/git/mmind/linux-rockchip.git for-next
config: x86_64-defconfig (attached as .config)
compiler: gcc-7 (Debian 7.5.0-3) 7.5.0
reproduce:
        # save the attached .config to linux build tree
        make ARCH=x86_64 

If you fix the issue, kindly add following tag
Reported-by: kbuild test robot <lkp@intel.com>

All warnings (new ones prefixed by >>):

   drivers//iommu/dma-iommu.c: In function '__iommu_dma_map':
>> drivers//iommu/dma-iommu.c:568:3: warning: ISO C90 forbids mixed declarations and code [-Wdeclaration-after-statement]
      void *padding_start = phys_to_virt(phys);
      ^~~~

vim +568 drivers//iommu/dma-iommu.c

   537	
   538	static dma_addr_t __iommu_dma_map(struct device *dev, phys_addr_t phys,
   539			size_t org_size, dma_addr_t dma_mask, bool coherent,
   540			enum dma_data_direction dir, unsigned long attrs)
   541	{
   542		int prot = dma_info_to_prot(dir, coherent, attrs);
   543		struct iommu_domain *domain = iommu_get_dma_domain(dev);
   544		struct iommu_dma_cookie *cookie = domain->iova_cookie;
   545		struct iova_domain *iovad = &cookie->iovad;
   546		size_t iova_off = iova_offset(iovad, phys);
   547		size_t aligned_size = iova_align(iovad, org_size + iova_off);
   548		dma_addr_t iova;
   549	
   550		if (unlikely(iommu_dma_deferred_attach(dev, domain)))
   551			return DMA_MAPPING_ERROR;
   552	
   553	#ifdef CONFIG_SWIOTLB
   554		/*
   555		 * If both the physical buffer start address and size are
   556		 * page aligned, we don't need to use a bounce page.
   557		 */
   558		if (iommu_needs_bounce_buffer(dev)
   559				&& !iova_offset(iovad, phys | org_size)) {
   560			phys = swiotlb_tbl_map_single(dev,
   561					__phys_to_dma(dev, io_tlb_start),
   562					phys, org_size, aligned_size, dir, attrs);
   563	
   564			if (phys == DMA_MAPPING_ERROR)
   565				return DMA_MAPPING_ERROR;
   566	
   567			/* Cleanup the padding area. */
 > 568			void *padding_start = phys_to_virt(phys);
   569			size_t padding_size = aligned_size;
   570	
   571			if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC) &&
   572			    (dir == DMA_TO_DEVICE ||
   573			     dir == DMA_BIDIRECTIONAL)) {
   574				padding_start += org_size;
   575				padding_size -= org_size;
   576			}
   577	
   578			memset(padding_start, 0, padding_size);
   579		}
   580	#endif
   581	
   582		iova = iommu_dma_alloc_iova(domain, aligned_size, dma_mask, dev);
   583		if (!iova)
   584			return DMA_MAPPING_ERROR;
   585	
   586		if (iommu_map_atomic(domain, iova, phys - iova_off, aligned_size,
   587					prot)) {
   588	
   589			if (unlikely(is_swiotlb_buffer(phys)))
   590				swiotlb_tbl_unmap_single(dev, phys, aligned_size,
   591						aligned_size, dir, attrs);
   592			iommu_dma_free_iova(cookie, iova, aligned_size, NULL);
   593			return DMA_MAPPING_ERROR;
   594		}
   595		return iova + iova_off;
   596	}
   597	

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