MIPS: ingenic: Add support for appended devicetree

Add support for booting the kernel from an externally-appended
devicetree, if no devicetree was built-in.

Signed-off-by: Paul Cercueil <[e-mail]>
Signed-off-by: Paul Burton <[e-mail]>
Cc: Ralf Baechle <[e-mail]>
Cc: James Hogan <[e-mail]>
Cc: [e-mail]
Cc: [e-mail]

arch/mips/Kconfig

···
 	select GPIOLIB
 	select COMMON_CLK
 	select GENERIC_IRQ_CHIP
-	select BUILTIN_DTB
+	select BUILTIN_DTB if MIPS_NO_APPENDED_DTB
 	select USE_OF
 	select LIBFDT
 

arch/mips/jz4740/setup.c

···
 
 #define JZ4740_EMC_SDRAM_CTRL 0x80
 
-
 static void __init jz4740_detect_mem(void)
 {
 	void __iomem *jz_emc_base;
···
 void __init plat_mem_setup(void)
 {
 	int offset;
+	void *dtb;
 
 	jz4740_reset_init();
-	__dt_setup_arch(__dtb_start);
 
-	offset = fdt_path_offset(__dtb_start, "/memory");
+	if (__dtb_start != __dtb_end)
+		dtb = __dtb_start;
+	else
+		dtb = (void *)fw_passed_dtb;
+
+	__dt_setup_arch(dtb);
+
+	offset = fdt_path_offset(dtb, "/memory");
 	if (offset < 0)
 		jz4740_detect_mem();
 
-	mips_machtype = get_board_mach_type(__dtb_start);
+	mips_machtype = get_board_mach_type(dtb);
 }
 
 void __init device_tree_init(void)