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Subject[PATCH 8/9] sparc/iommu: use __sbus_iommu_map_page to implement the map_sg path
Date
This means we handle > PAGE_SIZE offsets fine, and grow the size check
so far only performed in the map_page path. We lose the optimization
to not double flush a page if it apears in multiple consecutive SG list
entries. But at least for block I/O those don't happen anymore since
we properly merge in higher layers anyway.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reported-by: Guenter Roeck <linux@roeck-us.net>
---
arch/sparc/mm/iommu.c | 31 ++++++++++---------------------
1 file changed, 10 insertions(+), 21 deletions(-)

diff --git a/arch/sparc/mm/iommu.c b/arch/sparc/mm/iommu.c
index 37b5ce7657f6..8fbc08d14836 100644
--- a/arch/sparc/mm/iommu.c
+++ b/arch/sparc/mm/iommu.c
@@ -217,6 +217,11 @@ static dma_addr_t __sbus_iommu_map_page(struct device *dev, struct page *page,
if (!len || len > 256 * 1024)
return DMA_MAPPING_ERROR;

+ /*
+ * We expect unmapped highmem pages to be not in the cache.
+ * XXX Is this a good assumption?
+ * XXX What if someone else unmaps it here and races us?
+ */
if (per_page_flush && !PageHighMem(page)) {
unsigned long vaddr, p;

@@ -247,30 +252,14 @@ static int __sbus_iommu_map_sg(struct device *dev, struct scatterlist *sgl,
int nents, enum dma_data_direction dir, unsigned long attrs,
bool per_page_flush)
{
- unsigned long page, oldpage = 0;
struct scatterlist *sg;
- int i, j, n;
+ int j;

for_each_sg(sgl, sg, nents, j) {
- n = (sg->length + sg->offset + PAGE_SIZE-1) >> PAGE_SHIFT;
-
- /*
- * We expect unmapped highmem pages to be not in the cache.
- * XXX Is this a good assumption?
- * XXX What if someone else unmaps it here and races us?
- */
- if (per_page_flush && !PageHighMem(sg_page(sg))) {
- page = (unsigned long)page_address(sg_page(sg));
- for (i = 0; i < n; i++) {
- if (page != oldpage) { /* Already flushed? */
- flush_page_for_dma(page);
- oldpage = page;
- }
- page += PAGE_SIZE;
- }
- }
-
- sg->dma_address = iommu_get_one(dev, sg_phys(sg), n) + sg->offset;
+ sg->dma_address =__sbus_iommu_map_page(dev, sg_page(sg),
+ sg->offset, sg->length, per_page_flush);
+ if (sg->dma_address == DMA_MAPPING_ERROR)
+ return 0;
sg->dma_length = sg->length;
}

--
2.20.1
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