On Tue, Aug 19, 2025 at 08:36:53PM +0300, Leon Romanovsky wrote:
> From: Leon Romanovsky <leo...@nvidia.com>
>
> Extend base DMA page API to handle MMIO flow and follow
> existing dma_map_resource() implementation to rely on dma_map_direct()
> only to take DMA direct path.
I would reword this a little bit too
dma-mapping: implement DMA_ATTR_MMIO for dma_(un)map_page_attrs()
Make dma_map_page_attrs() and dma_map_page_attrs() respect
DMA_ATTR_MMIO.
DMA_ATR_MMIO makes the functions behave the same as dma_(un)map_resource():
- No swiotlb is possible
- Legacy dma_ops arches use ops->map_resource()
- No kmsan
- No arch_dma_map_phys_direct()
The prior patches have made the internl funtions called here support
DMA_ATTR_MMIO.
This is also preparation for turning dma_map_resource() into an inline
calling dma_map_phys(DMA_ATTR_MMIO) to consolidate the flows.
> @@ -166,14 +167,25 @@ dma_addr_t dma_map_page_attrs(struct device *dev,
> struct page *page,
> return DMA_MAPPING_ERROR;
>
> if (dma_map_direct(dev, ops) ||
> - arch_dma_map_phys_direct(dev, phys + size))
> + (!is_mmio && arch_dma_map_phys_direct(dev, phys + size)))
> addr = dma_direct_map_phys(dev, phys, size, dir, attrs);
PPC is the only user of arch_dma_map_phys_direct() and it looks like
it should be called on MMIO memory. Seems like another inconsistency
with map_resource. I'd leave it like the above though for this series.
> else if (use_dma_iommu(dev))
> addr = iommu_dma_map_phys(dev, phys, size, dir, attrs);
> - else
> + else if (is_mmio) {
> + if (!ops->map_resource)
> + return DMA_MAPPING_ERROR;
Probably written like:
if (ops->map_resource)
addr = ops->map_resource(dev, phys, size, dir, attrs);
else
addr = DMA_MAPPING_ERROR;
As I think some of the design here is to run the trace even on the
failure path?
Otherwise looks OK
Reviewed-by: Jason Gunthorpe <j...@nvidia.com>
Jason
