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    SubjectRe: [PATCH 04/15] swiotlb: remove unnecessary swiotlb_bus_to_virt
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    On Jul 9, 2009, at 8:04 PM, FUJITA Tomonori wrote:

    > swiotlb_bus_to_virt is unncessary; we can use swiotlb_bus_to_phys and
    > phys_to_virt instead.

    phys_to_virt (also, virt_to_phys) is invalid for highmem addresses on
    ppc. In most of the uses in this file, it doesn't matter, as the
    iotlb buffers themselves are alloc'd out of lowmem, but the
    dma_mark_clean() calls could happen on a highmem addr. Currently, on
    powerpc, dma_mark_clean() doesn't do anything, so it isn't a
    functional problem. I'm fine with the bulk of this patch, because in
    reality, if I need to do something with a virtual address of a highmem
    page, I have to get a kmap for the page. So the existing
    swiotlb_bus_to_virt isn't really helping.

    What is dma_mark_clean used for? Could it be made to take a paddr,
    and let the implementation deal with making sure there's a valid vaddr
    for the actual "clean" operation?

    I'd also like to see a comment with swiotlb_virt_to_bus() that notes
    that it should only be called on addresses in lowmem.

    Cheers,
    Becky

    >
    >
    > Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
    > ---
    > arch/powerpc/kernel/dma-swiotlb.c | 10 ----------
    > lib/swiotlb.c | 34 +++++++++++++++
    > +------------------
    > 2 files changed, 16 insertions(+), 28 deletions(-)
    >
    > diff --git a/arch/powerpc/kernel/dma-swiotlb.c b/arch/powerpc/kernel/
    > dma-swiotlb.c
    > index 68ccf11..41534ae 100644
    > --- a/arch/powerpc/kernel/dma-swiotlb.c
    > +++ b/arch/powerpc/kernel/dma-swiotlb.c
    > @@ -24,16 +24,6 @@
    > int swiotlb __read_mostly;
    > unsigned int ppc_swiotlb_enable;
    >
    > -void *swiotlb_bus_to_virt(struct device *hwdev, dma_addr_t addr)
    > -{
    > - unsigned long pfn = PFN_DOWN(swiotlb_bus_to_phys(hwdev, addr));
    > - void *pageaddr = page_address(pfn_to_page(pfn));
    > -
    > - if (pageaddr != NULL)
    > - return pageaddr + (addr % PAGE_SIZE);
    > - return NULL;
    > -}
    > -
    > dma_addr_t swiotlb_phys_to_bus(struct device *hwdev, phys_addr_t
    > paddr)
    > {
    > return paddr + get_dma_direct_offset(hwdev);
    > diff --git a/lib/swiotlb.c b/lib/swiotlb.c
    > index dc1cd1f..1a89c84 100644
    > --- a/lib/swiotlb.c
    > +++ b/lib/swiotlb.c
    > @@ -130,11 +130,6 @@ static dma_addr_t swiotlb_virt_to_bus(struct
    > device *hwdev,
    > return swiotlb_phys_to_bus(hwdev, virt_to_phys(address));
    > }
    >
    > -void * __weak swiotlb_bus_to_virt(struct device *hwdev, dma_addr_t
    > address)
    > -{
    > - return phys_to_virt(swiotlb_bus_to_phys(hwdev, address));
    > -}
    > -
    > int __weak swiotlb_arch_address_needs_mapping(struct device *hwdev,
    > dma_addr_t addr, size_t size)
    > {
    > @@ -307,9 +302,10 @@ address_needs_mapping(struct device *hwdev,
    > dma_addr_t addr, size_t size)
    > return swiotlb_arch_address_needs_mapping(hwdev, addr, size);
    > }
    >
    > -static int is_swiotlb_buffer(char *addr)
    > +static int is_swiotlb_buffer(phys_addr_t paddr)
    > {
    > - return addr >= io_tlb_start && addr < io_tlb_end;
    > + return paddr >= virt_to_phys(io_tlb_start) &&
    > + paddr < virt_to_phys(io_tlb_end);
    > }
    >
    > /*
    > @@ -582,11 +578,13 @@ EXPORT_SYMBOL(swiotlb_alloc_coherent);
    >
    > void
    > swiotlb_free_coherent(struct device *hwdev, size_t size, void *vaddr,
    > - dma_addr_t dma_handle)
    > + dma_addr_t dev_addr)
    > {
    > + phys_addr_t paddr = swiotlb_bus_to_phys(hwdev, dev_addr);
    > +
    > WARN_ON(irqs_disabled());
    > - if (!is_swiotlb_buffer(vaddr))
    > - free_pages((unsigned long) vaddr, get_order(size));
    > + if (!is_swiotlb_buffer(paddr))
    > + free_pages((unsigned long)vaddr, get_order(size));
    > else
    > /* DMA_TO_DEVICE to avoid memcpy in unmap_single */
    > do_unmap_single(hwdev, vaddr, size, DMA_TO_DEVICE);
    > @@ -671,19 +669,19 @@ EXPORT_SYMBOL_GPL(swiotlb_map_page);
    > static void unmap_single(struct device *hwdev, dma_addr_t dev_addr,
    > size_t size, int dir)
    > {
    > - char *dma_addr = swiotlb_bus_to_virt(hwdev, dev_addr);
    > + phys_addr_t paddr = swiotlb_bus_to_phys(hwdev, dev_addr);
    >
    > BUG_ON(dir == DMA_NONE);
    >
    > - if (is_swiotlb_buffer(dma_addr)) {
    > - do_unmap_single(hwdev, dma_addr, size, dir);
    > + if (is_swiotlb_buffer(paddr)) {
    > + do_unmap_single(hwdev, phys_to_virt(paddr), size, dir);
    > return;
    > }
    >
    > if (dir != DMA_FROM_DEVICE)
    > return;
    >
    > - dma_mark_clean(dma_addr, size);
    > + dma_mark_clean(phys_to_virt(paddr), size);
    > }
    >
    > void swiotlb_unmap_page(struct device *hwdev, dma_addr_t dev_addr,
    > @@ -708,19 +706,19 @@ static void
    > swiotlb_sync_single(struct device *hwdev, dma_addr_t dev_addr,
    > size_t size, int dir, int target)
    > {
    > - char *dma_addr = swiotlb_bus_to_virt(hwdev, dev_addr);
    > + phys_addr_t paddr = swiotlb_bus_to_phys(hwdev, dev_addr);
    >
    > BUG_ON(dir == DMA_NONE);
    >
    > - if (is_swiotlb_buffer(dma_addr)) {
    > - sync_single(hwdev, dma_addr, size, dir, target);
    > + if (is_swiotlb_buffer(paddr)) {
    > + sync_single(hwdev, phys_to_virt(paddr), size, dir, target);
    > return;
    > }
    >
    > if (dir != DMA_FROM_DEVICE)
    > return;
    >
    > - dma_mark_clean(dma_addr, size);
    > + dma_mark_clean(phys_to_virt(paddr), size);

    >
    > }
    >
    > void
    > --
    > 1.6.0.6
    >
    > --
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