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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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