u-boot/arch/arm/dts/sunxi-u-boot.dtsi

#include <config.h>

/*
 * This is the maximum size the U-Boot binary can be, which is basically
 * the start of the environment, minus the start of the U-Boot binary in
 * the MMC. This makes the assumption that the MMC is using 512-bytes
 * blocks, but devices using something other than that remains to be
 * seen.
 */
#define UBOOT_MMC_MAX_SIZE	(CONFIG_ENV_OFFSET - (CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_SECTOR * 512))

/ {
	binman {
		filename = "u-boot-sunxi-with-spl.bin";
		pad-byte = <0xff>;
		blob {
			filename = "spl/sunxi-spl.bin";
		};
		u-boot-img {
#ifdef CONFIG_MMC
			size = <UBOOT_MMC_MAX_SIZE>;
#endif
			pos = <CONFIG_SPL_PAD_TO>;
		};
	};
};