Allwinner NAND flashing
  =======================
  
  A lot of Allwinner devices, especially the older ones (pre-H3 era),
  comes with a NAND. NANDs storages are a pretty weak choice when it
  comes to the reliability, and it comes with a number of flaws like
  read and write disturbs, data retention issues, bloks becoming
  unusable, etc.
  
  In order to mitigate that, various strategies have been found to be
  able to recover from those issues like ECC, hardware randomization,
  and of course, redundancy for the critical parts.
  
  This is obviously something that we will take into account when
  creating our images. However, the BROM will use a quite weird pattern
  when accessing the NAND, and will access only at most 4kB per page,
  which means that we also have to split that binary accross several
  pages.
  
  In order to accomodate that, we create a tool that will generate an
  SPL image that is ready to be programmed directly embedding the ECCs,
  randomized, and with the necessary bits needed to reduce the number of
  bitflips. The U-Boot build system, when configured for the NAND will
  also generate the image sunxi-spl-with-ecc.bin that will have been
  generated by that tool.
  
  In order to flash your U-Boot image onto a board, assuming that the
  board is in FEL mode, you'll need the sunxi-tools that you can find at
  this repository: https://github.com/linux-sunxi/sunxi-tools
  
  Then, you'll need to first load an SPL to initialise the RAM:
  sunxi-fel spl spl/sunxi-spl.bin
  
  Load the binaries we'll flash into RAM:
  sunxi-fel write 0x4a000000 u-boot-dtb.bin
  sunxi-fel write 0x43000000 spl/sunxi-spl-with-ecc.bin
  
  And execute U-Boot
  sunxi-fel exe 0x4a000000
  
  On your board, you'll now have all the needed binaries into RAM, so
  you only need to erase the NAND...
  
  nand erase.chip
  
  Then write the SPL and its backup:
  
  nand write.raw.noverify 0x43000000 0 40
  nand write.raw.noverify 0x43000000 0x400000 40
  
  And finally write the U-Boot binary:
  nand write 0x4a000000 0x800000 0xc0000
  
  You can now reboot and enjoy your NAND.