swiotlb: refactor swiotlb_map_page

Remove the somewhat useless map_single function, and replace it with a
swiotlb_bounce_page handler that handles everything related to actually
bouncing a page.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

1 files changed, 30 insertions, 37 deletions

diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 15755d7a5242..57507b18caa4 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -544,26 +544,6 @@ found:
 }
 
 /*
- * Allocates bounce buffer and returns its physical address.
- */
-static phys_addr_t
-map_single(struct device *hwdev, phys_addr_t phys, size_t size,
-           enum dma_data_direction dir, unsigned long attrs)
-{
-        dma_addr_t start_dma_addr;
-
-        if (swiotlb_force == SWIOTLB_NO_FORCE) {
-                dev_warn_ratelimited(hwdev, "Cannot do DMA to address %pa\n",
-                                     &phys);
-                return SWIOTLB_MAP_ERROR;
-        }
-
-        start_dma_addr = __phys_to_dma(hwdev, io_tlb_start);
-        return swiotlb_tbl_map_single(hwdev, start_dma_addr, phys, size,
-                                      dir, attrs);
-}
-
-/*
  * tlb_addr is the physical address of the bounce buffer to unmap.
  */
 void swiotlb_tbl_unmap_single(struct device *hwdev, phys_addr_t tlb_addr,
@@ -714,6 +694,34 @@ static bool swiotlb_free_buffer(struct device *dev, size_t size,
         return true;
 }
 
+static dma_addr_t swiotlb_bounce_page(struct device *dev, phys_addr_t *phys,
+                size_t size, enum dma_data_direction dir, unsigned long attrs)
+{
+        dma_addr_t dma_addr;
+
+        if (unlikely(swiotlb_force == SWIOTLB_NO_FORCE)) {
+                dev_warn_ratelimited(dev,
+                        "Cannot do DMA to address %pa\n", phys);
+                return DIRECT_MAPPING_ERROR;
+        }
+
+        /* Oh well, have to allocate and map a bounce buffer. */
+        *phys = swiotlb_tbl_map_single(dev, __phys_to_dma(dev, io_tlb_start),
+                        *phys, size, dir, attrs);
+        if (*phys == SWIOTLB_MAP_ERROR)
+                return DIRECT_MAPPING_ERROR;
+
+        /* Ensure that the address returned is DMA'ble */
+        dma_addr = __phys_to_dma(dev, *phys);
+        if (unlikely(!dma_capable(dev, dma_addr, size))) {
+                swiotlb_tbl_unmap_single(dev, *phys, size, dir,
+                        attrs | DMA_ATTR_SKIP_CPU_SYNC);
+                return DIRECT_MAPPING_ERROR;
+        }
+
+        return dma_addr;
+}
+
 /*
  * Map a single buffer of the indicated size for DMA in streaming mode.  The
  * physical address to use is returned.
@@ -726,7 +734,7 @@ dma_addr_t swiotlb_map_page(struct device *dev, struct page *page,
                             enum dma_data_direction dir,
                             unsigned long attrs)
 {
-        phys_addr_t map, phys = page_to_phys(page) + offset;
+        phys_addr_t phys = page_to_phys(page) + offset;
         dma_addr_t dev_addr = phys_to_dma(dev, phys);
 
         BUG_ON(dir == DMA_NONE);
@@ -739,22 +747,7 @@ dma_addr_t swiotlb_map_page(struct device *dev, struct page *page,
                 return dev_addr;
 
         trace_swiotlb_bounced(dev, dev_addr, size, swiotlb_force);
-
-        /* Oh well, have to allocate and map a bounce buffer. */
-        map = map_single(dev, phys, size, dir, attrs);
-        if (map == SWIOTLB_MAP_ERROR)
-                return DIRECT_MAPPING_ERROR;
-
-        dev_addr = __phys_to_dma(dev, map);
-
-        /* Ensure that the address returned is DMA'ble */
-        if (dma_capable(dev, dev_addr, size))
-                return dev_addr;
-
-        attrs |= DMA_ATTR_SKIP_CPU_SYNC;
-        swiotlb_tbl_unmap_single(dev, map, size, dir, attrs);
-
-        return DIRECT_MAPPING_ERROR;
+        return swiotlb_bounce_page(dev, &phys, size, dir, attrs);
 }
 
 /*