scripts: sunxi: Build an raw SPL image

Introduce a new sunxi-spl-with-ecc.bin image with already the right header,
ECC, randomizer and padding for the BROM to be able to read it.

It needs to be flashed using a raw access to the NAND so that the
controller doesn't change a thing to it, since we already have all the
right parameters.

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Acked-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Reviewed-by: Heiko Schocher <hs@denx.de>

1 files changed, 54 insertions, 0 deletions

diff --git a/board/sunxi/README.nand b/board/sunxi/README.nand
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+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.
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