Re: [PATCH RFC 1/2] iommu/dma: skip swiotlb bounce for DMA_ATTR_MMIO in iommu_dma_map_phys

[Marek Szyprowski]

On 16.09.2026 17:23, Peng Fan (OSS) wrote:
> From: Peng Fan <peng.fan@xxxxxxx>
>
> MMIO resources mapped via dma_map_resource() carry DMA_ATTR_MMIO. These
> never need swiotlb bounce buffering, but the current code enters the
> swiotlb path when the physical address is not page-aligned, then rejects
> the mapping because MMIO cannot be bounced.
>
> Move the DMA_ATTR_MMIO check before the swiotlb block so the entire bounce
> path is skipped for MMIO, falling through directly to __iommu_dma_map()
> which creates the IOVA mapping.
>
> Fixes: f9374de14c0e8 ("iommu/dma: implement DMA_ATTR_MMIO for iommu_dma_(un)map_phys()")
> Assisted-by: Claude:claude-opus-4-6
> Signed-off-by: Peng Fan <peng.fan@xxxxxxx>


Applied only this patch to dma-mapping-fixes. Thanks!

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland