arm/xen: Introduce xen_setup_dma_ops()

This patch introduces new helper and places it in new header.
The helper's purpose is to assign any Xen specific DMA ops in
a single place. For now, we deal with xen-swiotlb DMA ops only.
The one of the subsequent commits in current series will add
xen-grant DMA ops case.

Also re-use the xen_swiotlb_detect() check on Arm32.

Signed-off-by: Oleksandr Tyshchenko <[e-mail]>
Reviewed-by: Stefano Stabellini <[e-mail]>
[For arm64]
Acked-by: Catalin Marinas <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Juergen Gross <[e-mail]>

arch/arm/include/asm/xen/xen-ops.h

···
+/* SPDX-License-Identifier: GPL-2.0 */
+#include <xen/arm/xen-ops.h>

arch/arm/mm/dma-mapping.c

···
 #include <asm/dma-iommu.h>
 #include <asm/mach/map.h>
 #include <asm/system_info.h>
-#include <xen/swiotlb-xen.h>
+#include <asm/xen/xen-ops.h>
 
 #include "dma.h"
 #include "mm.h"
···
 
 	set_dma_ops(dev, dma_ops);
 
-#ifdef CONFIG_XEN
-	if (xen_initial_domain())
-		dev->dma_ops = &xen_swiotlb_dma_ops;
-#endif
+	xen_setup_dma_ops(dev);
 	dev->archdata.dma_ops_setup = true;
 }
 

arch/arm64/include/asm/xen/xen-ops.h

···
+/* SPDX-License-Identifier: GPL-2.0 */
+#include <xen/arm/xen-ops.h>

arch/arm64/mm/dma-mapping.c

···
 #include <linux/dma-map-ops.h>
 #include <linux/dma-iommu.h>
 #include <xen/xen.h>
-#include <xen/swiotlb-xen.h>
 
 #include <asm/cacheflush.h>
+#include <asm/xen/xen-ops.h>
 
 void arch_sync_dma_for_device(phys_addr_t paddr, size_t size,
 		enum dma_data_direction dir)
···
 	if (iommu)
 		iommu_setup_dma_ops(dev, dma_base, dma_base + size - 1);
 
-#ifdef CONFIG_XEN
-	if (xen_swiotlb_detect())
-		dev->dma_ops = &xen_swiotlb_dma_ops;
-#endif
+	xen_setup_dma_ops(dev);
 }

include/xen/arm/xen-ops.h

···
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_ARM_XEN_OPS_H
+#define _ASM_ARM_XEN_OPS_H
+
+#include <xen/swiotlb-xen.h>
+
+static inline void xen_setup_dma_ops(struct device *dev)
+{
+#ifdef CONFIG_XEN
+	if (xen_swiotlb_detect())
+		dev->dma_ops = &xen_swiotlb_dma_ops;
+#endif
+}
+
+#endif /* _ASM_ARM_XEN_OPS_H */