swiotlb: remove swiotlb_dma_supported

The only user left is powerpc, but even there the generic dma-direct
version works just as well, given that we guarantee that the swiotlb
buffer must always be addressable.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Tested-by: Christian Zigotzky <chzigotzky@xenosoft.de>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/kernel/dma-swiotlb.c

@@ -36,7 +36,7 @@ const struct dma_map_ops powerpc_swiotlb_dma_ops = {
 	.free = __dma_nommu_free_coherent,
 	.map_sg = dma_direct_map_sg,
 	.unmap_sg = dma_direct_unmap_sg,
-	.dma_supported = swiotlb_dma_supported,
+	.dma_supported = dma_direct_supported,
 	.map_page = dma_direct_map_page,
 	.unmap_page = dma_direct_unmap_page,
 	.sync_single_for_cpu = dma_direct_sync_single_for_cpu,

include/linux/swiotlb.h

@@ -60,9 +60,6 @@ extern void swiotlb_tbl_sync_single(struct device *hwdev,
 				    size_t size, enum dma_data_direction dir,
 				    enum dma_sync_target target);
 
-extern int
-swiotlb_dma_supported(struct device *hwdev, u64 mask);
-
 #ifdef CONFIG_SWIOTLB
 extern enum swiotlb_force swiotlb_force;
 extern phys_addr_t io_tlb_start, io_tlb_end;

kernel/dma/swiotlb.c

@@ -648,15 +648,3 @@ bool swiotlb_map(struct device *dev, phys_addr_t *phys, dma_addr_t *dma_addr,
 
 	return true;
 }
-
-/*
- * Return whether the given device DMA address mask can be supported
- * properly.  For example, if your device can only drive the low 24-bits
- * during bus mastering, then you would pass 0x00ffffff as the mask to
- * this function.
- */
-int
-swiotlb_dma_supported(struct device *hwdev, u64 mask)
-{
-	return __phys_to_dma(hwdev, io_tlb_end - 1) <= mask;
-}