Re: [PATCH 1/2] powerpc/dma: Define map/unmap mmio resource callbacks

[Christoph Hellwig <hch@lst.de>]

>  		dma_direct_unmap_sg(dev, sglist, nelems, direction, attrs);
>  }
>  
> +static dma_addr_t dma_iommu_map_resource(struct device *dev,
> +					 phys_addr_t phys_addr, size_t size,
> +					 enum dma_data_direction dir,
> +					 unsigned long attrs)
> +{
> +	struct pci_dev *pdev = to_pci_dev(dev);
> +	struct pci_controller *phb = pci_bus_to_host(pdev->bus);
> +
> +	if (dma_iommu_map_bypass(dev, attrs)) {
> +		if (phb->controller_ops.dma_map_resource &&
> +		    phb->controller_ops.dma_map_resource(pdev, phys_addr, size,
> +							 dir))
> +			return DMA_MAPPING_ERROR;
> +		return dma_direct_map_resource(dev, phys_addr, size,
> +					       dir, attrs);
> +	}
> +	return DMA_MAPPING_ERROR;

Just a nitpick, but to the return errors early would be a much more
logical flow.  Also if the callback just decides if the mapping is
possible in bypass mode it should have that in the name:

	struct pci_controller_ops *ops = &phb->controller_ops;

	if (!dma_iommu_map_bypass(dev, attrs) ||
	    !ops->dma_can_direct_map_resource ||
	    !ops->dma_can_direct_map_resource(pdev, phys_addr, size, dir)
		return DMA_MAPPING_ERROR;
	return dma_direct_map_resource(dev, phys_addr, size, dir, attrs);

> +	if (dma_iommu_map_bypass(dev, attrs)) {
> +		if (phb->controller_ops.dma_unmap_resource)
> +			phb->controller_ops.dma_unmap_resource(pdev, dma_handle,
> +							size, dir);
> +	}

This can do a little early return as well, coupled with a WARN_ON_ONCE
as we should never end up in the unmap path for a setup where the map didn't
work.