On Wed, Oct 03, 2012 at 05:38:47PM -0700, Alexander Duyck wrote:
> In the case of swiotlb we already have the start of the region and the number
> of slabs that give us the region size. Instead of having to call
> virt_to_phys on two pointers we can just take advantage of the fact that the
> region is linear and just compute the end based on the start plus the size.
Why not take advantage of 'the fact that the region is linear' and just
pre-compute the end in swiotlb_init_with_tbl?
That way the logic in is_swiotlb_buffer is even simpler?
>
> Signed-off-by: Alexander Duyck <alexander.h.duyck@xxxxxxxxx>
> ---
>
> lib/swiotlb.c | 25 ++++++++++++-------------
> 1 files changed, 12 insertions(+), 13 deletions(-)
>
> diff --git a/lib/swiotlb.c b/lib/swiotlb.c
> index f114bf6..5cc4d4e 100644
> --- a/lib/swiotlb.c
> +++ b/lib/swiotlb.c
> @@ -57,11 +57,11 @@ int swiotlb_force;
> * swiotlb_tbl_sync_single_*, to see if the memory was in fact allocated by this
> * API.
> */
> -static char *io_tlb_start, *io_tlb_end;
> +static char *io_tlb_start;
>
> /*
> - * The number of IO TLB blocks (in groups of 64) between io_tlb_start and
> - * io_tlb_end. This is command line adjustable via setup_io_tlb_npages.
> + * The number of IO TLB blocks (in groups of 64).
> + * This is command line adjustable via setup_io_tlb_npages.
> */
> static unsigned long io_tlb_nslabs;
>
> @@ -128,11 +128,11 @@ void swiotlb_print_info(void)
> phys_addr_t pstart, pend;
>
> pstart = virt_to_phys(io_tlb_start);
> - pend = virt_to_phys(io_tlb_end);
> + pend = pstart + bytes;
>
> printk(KERN_INFO "software IO TLB [mem %#010llx-%#010llx] (%luMB) mapped at [%p-%p]\n",
> (unsigned long long)pstart, (unsigned long long)pend - 1,
> - bytes >> 20, io_tlb_start, io_tlb_end - 1);
> + bytes >> 20, io_tlb_start, io_tlb_start + bytes - 1);
> }
>
> void __init swiotlb_init_with_tbl(char *tlb, unsigned long nslabs, int verbose)
> @@ -143,12 +143,10 @@ void __init swiotlb_init_with_tbl(char *tlb, unsigned long nslabs, int verbose)
>
> io_tlb_nslabs = nslabs;
> io_tlb_start = tlb;
> - io_tlb_end = io_tlb_start + bytes;
>
> /*
> * Allocate and initialize the free list array. This array is used
> * to find contiguous free memory regions of size up to IO_TLB_SEGSIZE
> - * between io_tlb_start and io_tlb_end.
> */
> io_tlb_list = alloc_bootmem_pages(PAGE_ALIGN(io_tlb_nslabs * sizeof(int)));
> for (i = 0; i < io_tlb_nslabs; i++)
> @@ -254,14 +252,12 @@ swiotlb_late_init_with_tbl(char *tlb, unsigned long nslabs)
>
> io_tlb_nslabs = nslabs;
> io_tlb_start = tlb;
> - io_tlb_end = io_tlb_start + bytes;
>
> memset(io_tlb_start, 0, bytes);
>
> /*
> * Allocate and initialize the free list array. This array is used
> * to find contiguous free memory regions of size up to IO_TLB_SEGSIZE
> - * between io_tlb_start and io_tlb_end.
> */
> io_tlb_list = (unsigned int *)__get_free_pages(GFP_KERNEL,
> get_order(io_tlb_nslabs * sizeof(int)));
> @@ -304,7 +300,6 @@ cleanup3:
> sizeof(int)));
> io_tlb_list = NULL;
> cleanup2:
> - io_tlb_end = NULL;
> io_tlb_start = NULL;
> io_tlb_nslabs = 0;
> return -ENOMEM;
> @@ -339,8 +334,10 @@ void __init swiotlb_free(void)
>
> static int is_swiotlb_buffer(phys_addr_t paddr)
> {
> - return paddr >= virt_to_phys(io_tlb_start) &&
> - paddr < virt_to_phys(io_tlb_end);
> + phys_addr_t swiotlb_start = virt_to_phys(io_tlb_start);
> +
> + return paddr >= swiotlb_start &&
> + paddr < (swiotlb_start + (io_tlb_nslabs << IO_TLB_SHIFT));
> }
>
> /*
> @@ -938,6 +935,8 @@ EXPORT_SYMBOL(swiotlb_dma_mapping_error);
> int
> swiotlb_dma_supported(struct device *hwdev, u64 mask)
> {
> - return swiotlb_virt_to_bus(hwdev, io_tlb_end - 1) <= mask;
> + unsigned long bytes = io_tlb_nslabs << IO_TLB_SHIFT;
> +
> + return swiotlb_virt_to_bus(hwdev, io_tlb_start + bytes - 1) <= mask;
> }
> EXPORT_SYMBOL(swiotlb_dma_supported);
>
> --
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