Re: [PATCH v1 5/9] sparc64: Use physical address DMA mapping

[Jason Gunthorpe <jgg@xxxxxxxxxx>]

On Sun, Sep 28, 2025 at 06:02:25PM +0300, Leon Romanovsky wrote:
> @@ -273,13 +272,16 @@ static dma_addr_t dma_4u_map_page(struct device *dev, 
> struct page *page,
>       u32 bus_addr, ret;
>       unsigned long iopte_protection;
>  
> +     if (attrs & DMA_ATTR_MMIO)
> +             goto bad_no_ctx;
> +
>       iommu = dev->archdata.iommu;
>       strbuf = dev->archdata.stc;
>  
>       if (unlikely(direction == DMA_NONE))
>               goto bad_no_ctx;
>  
> -     oaddr = (unsigned long)(page_address(page) + offset);
> +     oaddr = (unsigned long)(phys_to_virt(phys));
>       npages = IO_PAGE_ALIGN(oaddr + sz) - (oaddr & IO_PAGE_MASK);
>       npages >>= IO_PAGE_SHIFT;

This should be cleaned up some more:

        oaddr = (unsigned long)(page_address(page) + offset);
        ret = bus_addr | (oaddr & ~IO_PAGE_MASK);

        base_paddr = __pa(oaddr & IO_PAGE_MASK);

Makes no sense to phys_to_virt() then __pa() on that result. Drop oaddr.

Then I would copy and paste the comment from mips about DMA_ATTR_MMIO
> @@ -367,13 +366,16 @@ static dma_addr_t dma_4v_map_page(struct device *dev, 
> struct page *page,
>       dma_addr_t bus_addr, ret;
>       long entry;
>  
> +     if (attrs & DMA_ATTR_MMIO)
> +             goto bad;
> +
>       iommu = dev->archdata.iommu;
>       atu = iommu->atu;
>  
>       if (unlikely(direction == DMA_NONE))
>               goto bad;
>  
> -     oaddr = (unsigned long)(page_address(page) + offset);
> +     oaddr = (unsigned long)(phys_to_virt(phys));
>       npages = IO_PAGE_ALIGN(oaddr + sz) - (oaddr & IO_PAGE_MASK);
>       npages >>= IO_PAGE_SHIFT;

Same remarks here

> +static dma_addr_t iounit_map_phys(struct device *dev, phys_addr_t phys,
> +             size_t len, enum dma_data_direction dir, unsigned long attrs)
>  {
> -     void *vaddr = page_address(page) + offset;
> +     void *vaddr = phys_to_virt(phys);
>       struct iounit_struct *iounit = dev->archdata.iommu;
>       unsigned long ret, flags;

iounit_get_area() does not seem to need vaddr:

        npages = ((vaddr & ~PAGE_MASK) + size + (PAGE_SIZE-1)) >> PAGE_SHIFT;

~PAGE_MASK is page_offset()

        iopte = MKIOPTE(__pa(vaddr & PAGE_MASK));

__pa(phys_to_virt(pa)) again:
  iopte = MKIOPTE(PAGE_ALIGN(pa));

        vaddr = IOUNIT_DMA_BASE + (scan << PAGE_SHIFT) + (vaddr & ~PAGE_MASK);

page_offset, then it replaces vaddr.

So I'd tidy this too.

> @@ -202,10 +204,10 @@ static dma_addr_t __sbus_iommu_map_page(struct device 
> *dev, struct page *page,
>        * We expect unmapped highmem pages to be not in the cache.
>        * XXX Is this a good assumption?
>        * XXX What if someone else unmaps it here and races us?
>        */

At least ARM32 has code that seems to say these assumptions are not
always true.. Oh well.

Jason