From 618d3adc351a24c4c48437c767befb88ca2d199d Mon Sep 17 00:00:00 2001 From: Jake Moilanen Date: Fri, 2 Mar 2007 15:49:43 -0600 Subject: [PATCH] [POWERPC] DMA 4GB boundary protection There are many adapters which can not handle DMAing acrosss any 4 GB boundary. For instance the latest Emulex adapters. This normally is not an issue as firmware gives us dma-windows under 4gigs. However, some of the new System-P boxes have dma-windows above 4gigs, and this present a problem. I propose fixing it in the IOMMU allocation instead of making each driver protect against it as it is more efficient, and won't require changing every driver which has not considered this issue. This patch checks to see if the mapping spans a 4 gig boundary, and if it does, retries the allocation. It tries the next allocation at the start of the crossed 4 gig boundary. Signed-off-by: Jake Moilanen Signed-off-by: Paul Mackerras --- arch/powerpc/kernel/iommu.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c index 95edad4faf..c50d7072f3 100644 --- a/arch/powerpc/kernel/iommu.c +++ b/arch/powerpc/kernel/iommu.c @@ -76,6 +76,7 @@ static unsigned long iommu_range_alloc(struct iommu_table *tbl, unsigned int align_order) { unsigned long n, end, i, start; + unsigned long start_addr, end_addr; unsigned long limit; int largealloc = npages > 15; int pass = 0; @@ -146,6 +147,15 @@ static unsigned long iommu_range_alloc(struct iommu_table *tbl, } } + /* DMA cannot cross 4 GB boundary */ + start_addr = (n + tbl->it_offset) << PAGE_SHIFT; + end_addr = (end + tbl->it_offset) << PAGE_SHIFT; + if ((start_addr >> 32) != (end_addr >> 32)) { + end_addr &= 0xffffffff00000000l; + start = (end_addr >> PAGE_SHIFT) - tbl->it_offset; + goto again; + } + for (i = n; i < end; i++) if (test_bit(i, tbl->it_map)) { start = i+1; -- 2.39.2