[PATCH] swiotlb: support syncing sub-ranges of mappings

This patch implements swiotlb_sync_single_range_for_{cpu,device}. This
is intended to support an x86_64 implementation of
dma_sync_single_range_for_{cpu,device}.

Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

include/asm-x86_64/swiotlb.h

@@ -15,6 +15,14 @@ extern void swiotlb_sync_single_for_cpu(struct device *hwdev,
 extern void swiotlb_sync_single_for_device(struct device *hwdev,
 					    dma_addr_t dev_addr,
 					    size_t size, int dir);
+extern void swiotlb_sync_single_range_for_cpu(struct device *hwdev,
+					      dma_addr_t dev_addr,
+					      unsigned long offset,
+					      size_t size, int dir);
+extern void swiotlb_sync_single_range_for_device(struct device *hwdev,
+						 dma_addr_t dev_addr,
+						 unsigned long offset,
+						 size_t size, int dir);
 extern void swiotlb_sync_sg_for_cpu(struct device *hwdev,
 				     struct scatterlist *sg, int nelems,
 				     int dir);

lib/swiotlb.c

@@ -622,6 +622,37 @@ swiotlb_sync_single_for_device(struct device *hwdev, dma_addr_t dev_addr,
 	swiotlb_sync_single(hwdev, dev_addr, size, dir);
 }
 
+/*
+ * Same as above, but for a sub-range of the mapping.
+ */
+static inline void
+swiotlb_sync_single_range(struct device *hwdev, dma_addr_t dev_addr,
+			  unsigned long offset, size_t size, int dir)
+{
+	char *dma_addr = phys_to_virt(dev_addr) + offset;
+
+	if (dir == DMA_NONE)
+		BUG();
+	if (dma_addr >= io_tlb_start && dma_addr < io_tlb_end)
+		sync_single(hwdev, dma_addr, size, dir);
+	else if (dir == DMA_FROM_DEVICE)
+		mark_clean(dma_addr, size);
+}
+
+void
+swiotlb_sync_single_range_for_cpu(struct device *hwdev, dma_addr_t dev_addr,
+				  unsigned long offset, size_t size, int dir)
+{
+	swiotlb_sync_single_range(hwdev, dev_addr, offset, size, dir);
+}
+
+void
+swiotlb_sync_single_range_for_device(struct device *hwdev, dma_addr_t dev_addr,
+				     unsigned long offset, size_t size, int dir)
+{
+	swiotlb_sync_single_range(hwdev, dev_addr, offset, size, dir);
+}
+
 /*
  * Map a set of buffers described by scatterlist in streaming mode for DMA.
  * This is the scatter-gather version of the above swiotlb_map_single
@@ -750,6 +781,8 @@ EXPORT_SYMBOL(swiotlb_map_sg);
 EXPORT_SYMBOL(swiotlb_unmap_sg);
 EXPORT_SYMBOL(swiotlb_sync_single_for_cpu);
 EXPORT_SYMBOL(swiotlb_sync_single_for_device);
+EXPORT_SYMBOL_GPL(swiotlb_sync_single_range_for_cpu);
+EXPORT_SYMBOL_GPL(swiotlb_sync_single_range_for_device);
 EXPORT_SYMBOL(swiotlb_sync_sg_for_cpu);
 EXPORT_SYMBOL(swiotlb_sync_sg_for_device);
 EXPORT_SYMBOL(swiotlb_dma_mapping_error);