arm64: introduce is_device_dma_coherent

Introduce a boolean flag and an accessor function to check whether a
device is dma_coherent. Set the flag from set_arch_dma_coherent_ops.
Signed-off-by: NStefano Stabellini <stefano.stabellini@eu.citrix.com>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>
Reviewed-by: NCatalin Marinas <catalin.marinas@arm.com>

arch/arm64/include/asm/device.h

@@ -21,6 +21,7 @@ struct dev_archdata {
 #ifdef CONFIG_IOMMU_API
 	void *iommu;			/* private IOMMU data */
 #endif
+	bool dma_coherent;
 };
 
 struct pdev_archdata {

arch/arm64/include/asm/dma-mapping.h

@@ -54,11 +54,18 @@ static inline void set_dma_ops(struct device *dev, struct dma_map_ops *ops)
 
 static inline int set_arch_dma_coherent_ops(struct device *dev)
 {
+	dev->archdata.dma_coherent = true;
 	set_dma_ops(dev, &coherent_swiotlb_dma_ops);
 	return 0;
 }
 #define set_arch_dma_coherent_ops	set_arch_dma_coherent_ops
 
+/* do not use this function in a driver */
+static inline bool is_device_dma_coherent(struct device *dev)
+{
+	return dev->archdata.dma_coherent;
+}
+
 #include <asm-generic/dma-mapping-common.h>
 
 static inline dma_addr_t phys_to_dma(struct device *dev, phys_addr_t paddr)