ARM/u-boot: Add support for FDTs passed in the uImage

Since we're using multi-part uImage format, we can add the FDT as
a seperate "blob" in the uImage, if the used U-Boot version is not
"FDT enabled".

This is used for example for our Verdex target. Currently I've got
a local hack in the platform/u-boot/Jamfile, looking into pulling
in the FDT files and a proper Jam setup to do that properly...

headers/private/kernel/boot/platform/u-boot/platform_stage2_args.h

@@ -12,6 +12,8 @@
 struct platform_stage2_args {
 	void *boot_tgz_data;
 	uint32 boot_tgz_size;
+	void *fdt_data;
+	uint32 fdt_size;
 };
 
 #endif	/* KERNEL_BOOT_PLATFORM_UBOOT_STAGE2_H */

src/system/boot/platform/u-boot/start.cpp

@@ -172,11 +172,33 @@ start_raw(int argc, const char **argv)
 	args.arguments = NULL;
 	args.platform.boot_tgz_data = NULL;
 	args.platform.boot_tgz_size = 0;
+	args.platform.fdt_data = NULL;
+	args.platform.fdt_size = 0;
+
+	// if we get passed a uimage, try to find the third blob only if we do not have FDT data yet
+	if (gUImage != NULL
+		&& !gFDT
+		&& image_multi_getimg(gUImage, 2,
+			(uint32*)&args.platform.fdt_data,
+			&args.platform.fdt_size)) {
+		// found a blob, assume it is FDT data, when working on a platform
+		// which does not have an FDT enabled U-Boot
+		gFDT = args.platform.fdt_data;
+	}
 
 	serial_init(gFDT);
 	console_init();
 	cpu_init();
 
+	if (args.platform.fdt_data) {
+		dprintf("Found FDT from uimage @ %p, %" B_PRIu32 " bytes\n",
+			args.platform.fdt_data, args.platform.fdt_size);
+	} else if (gFDT) {
+		/* Fixup args so we can pass the gFDT on to the kernel */
+		args.platform.fdt_data = gFDT;
+		args.platform.fdt_size = fdt_totalsize(gFDT);
+	}
+
 	// if we get passed an FDT, check /chosen for initrd
 	if (gFDT != NULL) {
 		int node = fdt_path_offset(gFDT, "/chosen");