dma-mapping: Add helpers for dma_range_map bounds

Several places want to compute the lower and/or upper bounds of a
dma_range_map, so let's factor that out into reusable helpers.
Acked-by: Rob Herring <robh@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hanjun Guo <guohanjun@huawei.com> # For arm64
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Tested-by: Hanjun Guo <guohanjun@huawei.com>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/45ec52f033ec4dfb364e23f48abaf787f612fa53.1713523152.git.robin.murphy@arm.comSigned-off-by: Joerg Roedel <jroedel@suse.de>

arch/loongarch/kernel/dma.c

@@ -8,17 +8,12 @@
 void acpi_arch_dma_setup(struct device *dev)
 {
 	int ret;
-	u64 mask, end = 0;
+	u64 mask, end;
 	const struct bus_dma_region *map = NULL;
 
 	ret = acpi_dma_get_range(dev, &map);
 	if (!ret && map) {
-		const struct bus_dma_region *r = map;
-
-		for (end = 0; r->size; r++) {
-			if (r->dma_start + r->size - 1 > end)
-				end = r->dma_start + r->size - 1;
-		}
+		end = dma_range_map_max(map);
 
 		mask = DMA_BIT_MASK(ilog2(end) + 1);
 		dev->bus_dma_limit = end;

drivers/acpi/arm64/dma.c

@@ -28,13 +28,7 @@ void acpi_arch_dma_setup(struct device *dev)
 
 	ret = acpi_dma_get_range(dev, &map);
 	if (!ret && map) {
-		const struct bus_dma_region *r = map;
-
-		for (end = 0; r->size; r++) {
-			if (r->dma_start + r->size - 1 > end)
-				end = r->dma_start + r->size - 1;
-		}
-
+		end = dma_range_map_max(map);
 		dev->dma_range_map = map;
 	}
 

drivers/of/device.c

@@ -117,16 +117,9 @@ int of_dma_configure_id(struct device *dev, struct device_node *np,
 		if (!force_dma)
 			return ret == -ENODEV ? 0 : ret;
 	} else {
-		const struct bus_dma_region *r = map;
-
 		/* Determine the overall bounds of all DMA regions */
-		for (dma_start = ~0; r->size; r++) {
-			/* Take lower and upper limits */
-			if (r->dma_start < dma_start)
-				dma_start = r->dma_start;
-			if (r->dma_start + r->size > end)
-				end = r->dma_start + r->size;
-		}
+		dma_start = dma_range_map_min(map);
+		end = dma_range_map_max(map);
 	}
 
 	/*

include/linux/dma-direct.h

@@ -54,6 +54,24 @@ static inline phys_addr_t translate_dma_to_phys(struct device *dev,
 	return (phys_addr_t)-1;
 }
 
+static inline dma_addr_t dma_range_map_min(const struct bus_dma_region *map)
+{
+	dma_addr_t ret = (dma_addr_t)U64_MAX;
+
+	for (; map->size; map++)
+		ret = min(ret, map->dma_start);
+	return ret;
+}
+
+static inline dma_addr_t dma_range_map_max(const struct bus_dma_region *map)
+{
+	dma_addr_t ret = 0;
+
+	for (; map->size; map++)
+		ret = max(ret, map->dma_start + map->size - 1);
+	return ret;
+}
+
 #ifdef CONFIG_ARCH_HAS_PHYS_TO_DMA
 #include <asm/dma-direct.h>
 #ifndef phys_to_dma_unencrypted