[PATCH -mm 3/4] swiotlb: respect the segment boundary limits

FUJITA Tomonori
2007-11-22T02:48:06Z

This patch makes swiotlb not allocate a memory area spanning LLD's
segment boundary.

is_span_boundary() judges whether a memory area spans LLD's segment
boundary. If map_single finds such a area, map_single tries to find
the next available memory area.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
---
lib/swiotlb.c | 41 +++++++++++++++++++++++++++++++++++------
1 files changed, 35 insertions(+), 6 deletions(-)

diff --git a/lib/swiotlb.c b/lib/swiotlb.c
index 1a8050a..4bb5a11 100644
--- a/lib/swiotlb.c
+++ b/lib/swiotlb.c
@@ -282,6 +282,15 @@ address_needs_mapping(struct device *hwdev, dma_addr_t addr)
return (addr & ~mask) != 0;
}

+static inline unsigned int is_span_boundary(unsigned int index,
+ unsigned int nslots,
+ unsigned long offset_slots,
+ unsigned long max_slots)
+{
+ unsigned long offset = (offset_slots + index) & (max_slots - 1);
+ return offset + nslots > max_slots;
+}
+
/*
* Allocates bounce buffer and returns its kernel virtual address.
*/
@@ -292,6 +301,16 @@ map_single(struct device *hwdev, char *buffer, size_t size, int dir)
char *dma_addr;
unsigned int nslots, stride, index, wrap;
int i;
+ unsigned long start_dma_addr;
+ unsigned long mask;
+ unsigned long offset_slots;
+ unsigned long max_slots;
+
+ mask = dma_get_seg_boundary(hwdev);
+ start_dma_addr = virt_to_bus(io_tlb_start) & mask;
+
+ offset_slots = ALIGN(start_dma_addr, 1 << IO_TLB_SHIFT) >> IO_TLB_SHIFT;
+ max_slots = ALIGN(mask + 1, 1 << IO_TLB_SHIFT) >> IO_TLB_SHIFT;

/*
* For mappings greater than a page, we limit the stride (and
@@ -311,10 +330,17 @@ map_single(struct device *hwdev, char *buffer, size_t size, int dir)
*/
spin_lock_irqsave(&io_tlb_lock, flags);
{
- wrap = index = ALIGN(io_tlb_index, stride);
-
+ index = ALIGN(io_tlb_index, stride);
if (index >= io_tlb_nslabs)
- wrap = index = 0;
+ index = 0;
+
+ while (is_span_boundary(index, nslots, offset_slots,
+ max_slots)) {
+ index += stride;
+ if (index >= io_tlb_nslabs)
+ index = 0;
+ }
+ wrap = index;

do {
/*
@@ -341,9 +367,12 @@ map_single(struct device *hwdev, char *buffer, size_t size, int dir)

goto found;
}
- index += stride;
- if (index >= io_tlb_nslabs)
- index = 0;
+ do {
+ index += stride;
+ if (index >= io_tlb_nslabs)
+ index = 0;
+ } while (is_span_boundary(index, nslots, offset_slots,
+ max_slots));
} while (index != wrap);

spin_unlock_irqrestore(&io_tlb_lock, flags);
--
1.5.3.4