x86: remove arch specific dma_supported implementation

And instead wire it up as method for all the dma_map_ops instances.

Note that this also means the arch specific check will be fully instead
of partially applied in the AMD iommu driver.

Signed-off-by: Christoph Hellwig <hch@lst.de>

arch/x86/kernel/amd_gart_64.c

@@ -704,6 +704,7 @@ static const struct dma_map_ops gart_dma_ops = {
 	.alloc				= gart_alloc_coherent,
 	.free				= gart_free_coherent,
 	.mapping_error			= gart_mapping_error,
+	.dma_supported			= x86_dma_supported,
 };
 
 static void gart_iommu_shutdown(void)

arch/x86/kernel/pci-calgary_64.c

@@ -493,6 +493,7 @@ static const struct dma_map_ops calgary_dma_ops = {
 	.map_page = calgary_map_page,
 	.unmap_page = calgary_unmap_page,
 	.mapping_error = calgary_mapping_error,
+	.dma_supported = x86_dma_supported,
 };
 
 static inline void __iomem * busno_to_bbar(unsigned char num)

arch/x86/kernel/pci-dma.c

@@ -213,10 +213,8 @@ static __init int iommu_setup(char *p)
 }
 early_param("iommu", iommu_setup);
 
-int dma_supported(struct device *dev, u64 mask)
+int x86_dma_supported(struct device *dev, u64 mask)
 {
-	const struct dma_map_ops *ops = get_dma_ops(dev);
-
 #ifdef CONFIG_PCI
 	if (mask > 0xffffffff && forbid_dac > 0) {
 		dev_info(dev, "PCI: Disallowing DAC for device\n");
@@ -224,9 +222,6 @@ int dma_supported(struct device *dev, u64 mask)
 	}
 #endif
 
-	if (ops->dma_supported)
-		return ops->dma_supported(dev, mask);
-
 	/* Copied from i386. Doesn't make much sense, because it will
 	   only work for pci_alloc_coherent.
 	   The caller just has to use GFP_DMA in this case. */
@@ -252,7 +247,6 @@ int dma_supported(struct device *dev, u64 mask)
 
 	return 1;
 }
-EXPORT_SYMBOL(dma_supported);
 
 static int __init pci_iommu_init(void)
 {

arch/x86/kernel/pci-nommu.c

@@ -104,4 +104,5 @@ const struct dma_map_ops nommu_dma_ops = {
 	.sync_sg_for_device	= nommu_sync_sg_for_device,
 	.is_phys		= 1,
 	.mapping_error		= nommu_mapping_error,
+	.dma_supported		= x86_dma_supported,
 };