dma-mapping, powerpc: simplify the arch dma_set_mask override

Instead of letting the architecture supply all of dma_set_mask just
give it an additional hook selected by Kconfig.

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/Makefile

@@ -105,6 +105,7 @@ obj-$(CONFIG_UPROBES)		+= uprobes.o
 obj-$(CONFIG_PPC_UDBG_16550)	+= legacy_serial.o udbg_16550.o
 obj-$(CONFIG_STACKTRACE)	+= stacktrace.o
 obj-$(CONFIG_SWIOTLB)		+= dma-swiotlb.o
+obj-$(CONFIG_ARCH_HAS_DMA_SET_MASK) += dma-mask.o
 
 pci64-$(CONFIG_PPC64)		+= pci_dn.o pci-hotplug.o isa-bridge.o
 obj-$(CONFIG_PCI)		+= pci_$(BITS).o $(pci64-y) \

arch/powerpc/kernel/dma-mask.c

@@ -0,0 +1,12 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/dma-mapping.h>
+#include <linux/export.h>
+#include <asm/machdep.h>
+
+void arch_dma_set_mask(struct device *dev, u64 dma_mask)
+{
+	if (ppc_md.dma_set_mask)
+		ppc_md.dma_set_mask(dev, dma_mask);
+}
+EXPORT_SYMBOL(arch_dma_set_mask);

arch/powerpc/kernel/dma.c

@@ -234,18 +234,6 @@ const struct dma_map_ops dma_nommu_ops = {
 };
 EXPORT_SYMBOL(dma_nommu_ops);
 
-int dma_set_mask(struct device *dev, u64 dma_mask)
-{
-	if (ppc_md.dma_set_mask)
-		return ppc_md.dma_set_mask(dev, dma_mask);
-
-	if (!dev->dma_mask || !dma_supported(dev, dma_mask))
-		return -EIO;
-	*dev->dma_mask = dma_mask;
-	return 0;
-}
-EXPORT_SYMBOL(dma_set_mask);
-
 static int __init dma_init(void)
 {
 #ifdef CONFIG_IBMVIO