NAND flashing tool used to flash SPL and U-boot. SPL should be flashed to first four blocks as in AM335x, RBL checks for SPL at 1st 4 Blocks. If the 1st block fails, RBL checks in 2nd blocks and so on till 4th Block. To support this feature, SPL needs to be flashed to 1st 4 blocks. So the offset for flashing SPL are 0x0, 0x20000, 0x40000 & 0x60000. For U-Boot flashing offset to 0x80000, on the 4th block. Flash layout of NAND is shown