of: Introduce of_translate_dma_region()

This function is similar to of_translate_dma_address() but also reads a
length in addition to an address from a device tree property.
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Link: https://lore.kernel.org/r/20230120174251.4004100-2-thierry.reding@gmail.comSigned-off-by: Joerg Roedel <jroedel@suse.de>

drivers/of/address.c

@@ -626,6 +626,47 @@ u64 of_translate_dma_address(struct device_node *dev, const __be32 *in_addr)
 }
 EXPORT_SYMBOL(of_translate_dma_address);
 
+/**
+ * of_translate_dma_region - Translate device tree address and size tuple
+ * @dev: device tree node for which to translate
+ * @prop: pointer into array of cells
+ * @start: return value for the start of the DMA range
+ * @length: return value for the length of the DMA range
+ *
+ * Returns a pointer to the cell immediately following the translated DMA region.
+ */
+const __be32 *of_translate_dma_region(struct device_node *dev, const __be32 *prop,
+				      phys_addr_t *start, size_t *length)
+{
+	struct device_node *parent;
+	u64 address, size;
+	int na, ns;
+
+	parent = __of_get_dma_parent(dev);
+	if (!parent)
+		return NULL;
+
+	na = of_bus_n_addr_cells(parent);
+	ns = of_bus_n_size_cells(parent);
+
+	of_node_put(parent);
+
+	address = of_translate_dma_address(dev, prop);
+	if (address == OF_BAD_ADDR)
+		return NULL;
+
+	size = of_read_number(prop + na, ns);
+
+	if (start)
+		*start = address;
+
+	if (length)
+		*length = size;
+
+	return prop + na + ns;
+}
+EXPORT_SYMBOL(of_translate_dma_region);
+
 const __be32 *__of_get_address(struct device_node *dev, int index, int bar_no,
 			       u64 *size, unsigned int *flags)
 {

include/linux/of_address.h

@@ -38,6 +38,8 @@ struct of_pci_range {
 /* Translate a DMA address from device space to CPU space */
 extern u64 of_translate_dma_address(struct device_node *dev,
 				    const __be32 *in_addr);
+extern const __be32 *of_translate_dma_region(struct device_node *dev, const __be32 *addr,
+					     phys_addr_t *start, size_t *length);
 
 #ifdef CONFIG_OF_ADDRESS
 extern u64 of_translate_address(struct device_node *np, const __be32 *addr);