fdt: Add a function to decode a named memory region

Permit decoding of a named memory region from the device tree. This allows
easy run-time configuration of the address of on-chip SRAM, SDRAM, etc.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@ti.com>

include/fdtdec.h

@@ -677,4 +677,31 @@ int fdt_get_named_resource(const void *fdt, int node, const char *property,
  */
 int fdtdec_pci_get_bdf(const void *fdt, int node, int *bdf);
 
+/**
+ * Decode a named region within a memory bank of a given type.
+ *
+ * This function handles selection of a memory region. The region is
+ * specified as an offset/size within a particular type of memory.
+ *
+ * The properties used are:
+ *
+ *	<mem_type>-memory<suffix> for the name of the memory bank
+ *	<mem_type>-offset<suffix> for the offset in that bank
+ *
+ * The property value must have an offset and a size. The function checks
+ * that the region is entirely within the memory bank.5
+ *
+ * @param blob		FDT blob
+ * @param node		Node containing the properties (-1 for /config)
+ * @param mem_type	Type of memory to use, which is a name, such as
+ *			"u-boot" or "kernel".
+ * @param suffix	String to append to the memory/offset
+ *			property names
+ * @param basep		Returns base of region
+ * @param sizep		Returns size of region
+ * @return 0 if OK, -ive on error
+ */
+int fdtdec_decode_memory_region(const void *blob, int node,
+				const char *mem_type, const char *suffix,
+				fdt_addr_t *basep, fdt_size_t *sizep);
 #endif

lib/fdtdec.c

@@ -793,4 +793,65 @@ int fdtdec_pci_get_bdf(const void *fdt, int node, int *bdf)
 
 	return 0;
 }
+
+int fdtdec_decode_memory_region(const void *blob, int config_node,
+				const char *mem_type, const char *suffix,
+				fdt_addr_t *basep, fdt_size_t *sizep)
+{
+	char prop_name[50];
+	const char *mem;
+	fdt_size_t size, offset_size;
+	fdt_addr_t base, offset;
+	int node;
+
+	if (config_node == -1) {
+		config_node = fdt_path_offset(blob, "/config");
+		if (config_node < 0) {
+			debug("%s: Cannot find /config node\n", __func__);
+			return -ENOENT;
+		}
+	}
+	if (!suffix)
+		suffix = "";
+
+	snprintf(prop_name, sizeof(prop_name), "%s-memory%s", mem_type,
+		 suffix);
+	mem = fdt_getprop(blob, config_node, prop_name, NULL);
+	if (!mem) {
+		debug("%s: No memory type for '%s', using /memory\n", __func__,
+		      prop_name);
+		mem = "/memory";
+	}
+
+	node = fdt_path_offset(blob, mem);
+	if (node < 0) {
+		debug("%s: Failed to find node '%s': %s\n", __func__, mem,
+		      fdt_strerror(node));
+		return -ENOENT;
+	}
+
+	/*
+	 * Not strictly correct - the memory may have multiple banks. We just
+	 * use the first
+	 */
+	if (fdtdec_decode_region(blob, node, "reg", &base, &size)) {
+		debug("%s: Failed to decode memory region %s\n", __func__,
+		      mem);
+		return -EINVAL;
+	}
+
+	snprintf(prop_name, sizeof(prop_name), "%s-offset%s", mem_type,
+		 suffix);
+	if (fdtdec_decode_region(blob, config_node, prop_name, &offset,
+				 &offset_size)) {
+		debug("%s: Failed to decode memory region '%s'\n", __func__,
+		      prop_name);
+		return -EINVAL;
+	}
+
+	*basep = base + offset;
+	*sizep = offset_size;
+
+	return 0;
+}
 #endif