[Xen-devel] [PATCH 3/4] swiotlb-xen: simplify the DMA sync method implementations

[Christoph Hellwig <hch@xxxxxx>]

Get rid of the grand multiplexer and implement the sync_single_for_cpu
and sync_single_for_device methods directly, and then loop over them
for the scatterlist based variants.

Note that this also loses a few comments related to highlevel DMA API
concepts, which have nothing to do with the swiotlb-xen implementation
details.

Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
 drivers/xen/swiotlb-xen.c | 84 +++++++++++++--------------------------
 1 file changed, 28 insertions(+), 56 deletions(-)

diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
index 97a55c225593..9a951504dc12 100644
--- a/drivers/xen/swiotlb-xen.c
+++ b/drivers/xen/swiotlb-xen.c
@@ -455,48 +455,28 @@ static void xen_swiotlb_unmap_page(struct device *hwdev, 
dma_addr_t dev_addr,
        xen_unmap_single(hwdev, dev_addr, size, dir, attrs);
 }
 
-/*
- * Make physical memory consistent for a single streaming mode DMA translation
- * after a transfer.
- *
- * If you perform a xen_swiotlb_map_page() but wish to interrogate the buffer
- * using the cpu, yet do not wish to teardown the dma mapping, you must
- * call this function before doing so.  At the next point you give the dma
- * address back to the card, you must first perform a
- * xen_swiotlb_dma_sync_for_device, and then the device again owns the buffer
- */
 static void
-xen_swiotlb_sync_single(struct device *hwdev, dma_addr_t dev_addr,
-                       size_t size, enum dma_data_direction dir,
-                       enum dma_sync_target target)
+xen_swiotlb_sync_single_for_cpu(struct device *dev, dma_addr_t dma_addr,
+               size_t size, enum dma_data_direction dir)
 {
-       phys_addr_t paddr = xen_bus_to_phys(dev_addr);
+       phys_addr_t paddr = xen_bus_to_phys(dma_addr);
 
-       BUG_ON(dir == DMA_NONE);
-
-       if (target == SYNC_FOR_CPU)
-               xen_dma_sync_single_for_cpu(hwdev, dev_addr, size, dir);
+       xen_dma_sync_single_for_cpu(dev, dma_addr, size, dir);
 
-       /* NOTE: We use dev_addr here, not paddr! */
-       if (is_xen_swiotlb_buffer(dev_addr))
-               swiotlb_tbl_sync_single(hwdev, paddr, size, dir, target);
-
-       if (target == SYNC_FOR_DEVICE)
-               xen_dma_sync_single_for_device(hwdev, dev_addr, size, dir);
+       if (is_xen_swiotlb_buffer(dma_addr))
+               swiotlb_tbl_sync_single(dev, paddr, size, dir, SYNC_FOR_CPU);
 }
 
-void
-xen_swiotlb_sync_single_for_cpu(struct device *hwdev, dma_addr_t dev_addr,
-                               size_t size, enum dma_data_direction dir)
+static void
+xen_swiotlb_sync_single_for_device(struct device *dev, dma_addr_t dma_addr,
+               size_t size, enum dma_data_direction dir)
 {
-       xen_swiotlb_sync_single(hwdev, dev_addr, size, dir, SYNC_FOR_CPU);
-}
+       phys_addr_t paddr = xen_bus_to_phys(dma_addr);
 
-void
-xen_swiotlb_sync_single_for_device(struct device *hwdev, dma_addr_t dev_addr,
-                                  size_t size, enum dma_data_direction dir)
-{
-       xen_swiotlb_sync_single(hwdev, dev_addr, size, dir, SYNC_FOR_DEVICE);
+       if (is_xen_swiotlb_buffer(dma_addr))
+               swiotlb_tbl_sync_single(dev, paddr, size, dir, SYNC_FOR_DEVICE);
+
+       xen_dma_sync_single_for_device(dev, dma_addr, size, dir);
 }
 
 /*
@@ -541,38 +521,30 @@ xen_swiotlb_map_sg(struct device *dev, struct scatterlist 
*sgl, int nelems,
        return 0;
 }
 
-/*
- * Make physical memory consistent for a set of streaming mode DMA translations
- * after a transfer.
- *
- * The same as swiotlb_sync_single_* but for a scatter-gather list, same rules
- * and usage.
- */
 static void
-xen_swiotlb_sync_sg(struct device *hwdev, struct scatterlist *sgl,
-                   int nelems, enum dma_data_direction dir,
-                   enum dma_sync_target target)
+xen_swiotlb_sync_sg_for_cpu(struct device *dev, struct scatterlist *sgl,
+                           int nelems, enum dma_data_direction dir)
 {
        struct scatterlist *sg;
        int i;
 
-       for_each_sg(sgl, sg, nelems, i)
-               xen_swiotlb_sync_single(hwdev, sg->dma_address,
-                                       sg_dma_len(sg), dir, target);
-}
-
-static void
-xen_swiotlb_sync_sg_for_cpu(struct device *hwdev, struct scatterlist *sg,
-                           int nelems, enum dma_data_direction dir)
-{
-       xen_swiotlb_sync_sg(hwdev, sg, nelems, dir, SYNC_FOR_CPU);
+       for_each_sg(sgl, sg, nelems, i) {
+               xen_swiotlb_sync_single_for_cpu(dev, sg->dma_address,
+                               sg->length, dir);
+       }
 }
 
 static void
-xen_swiotlb_sync_sg_for_device(struct device *hwdev, struct scatterlist *sg,
+xen_swiotlb_sync_sg_for_device(struct device *dev, struct scatterlist *sgl,
                               int nelems, enum dma_data_direction dir)
 {
-       xen_swiotlb_sync_sg(hwdev, sg, nelems, dir, SYNC_FOR_DEVICE);
+       struct scatterlist *sg;
+       int i;
+
+       for_each_sg(sgl, sg, nelems, i) {
+               xen_swiotlb_sync_single_for_device(dev, sg->dma_address,
+                               sg->length, dir);
+       }
 }
 
 /*
-- 
2.20.1


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