binaries: add FEL capable SPL binaries

FEL booting allows to boot a board using an USB OTG connection from a
host PC, without the need to use any media (SD card) or on-board storage
(SPI flash). This is controlled by the BootROM, which runs entirely in
AArch32 mode. To allow FEL booting, we need to load and execute some code
to at least initialise the DRAM. U-Boot's SPL can do this, but it needs
to return to the (32 bit!) BootROM to allow loading of further firmware
components or other images.
Since the mainline U-Boot is an AArch64 port, this is not easily doable
with the upstream version. However it is possible to build an AArch32
version of the SPL, with the help of some (non-upstream) patches [1].

Add three binaries to allow FEL booting of A64 (DDR3/LPDDR3 DRAM) and
H5 boards.
Also document the steps required to rebuild those binaries.

[1] https://github.com/apritzel/u-boot/commits/sunxi64-fel32

Author: apritzel

binaries/README.md

@@ -39,3 +39,38 @@ To rebuild those binaries, fetch the allwinner branch from the
 The resulting binary is `build/sun50iw1p1/debug/bl31.bin`. For the non-debug
 build, use `DEBUG=0` in the command line above and use the binary at
 `build/sun50iw1p1/release/bl31.bin`.
+
+FEL capable SPL builds
+----------------------
+- `sunxi-a64-spl32-ddr3.bin`: 32bit build of a mainline based U-Boot SPL. Can be
+used for FEL booting. This version is for boards with the Allwinner A64 SoC
+and DDR3 DRAM (*not* LPDDR3), like the original Pine64 or the BananaPi M64.
+- `sunxi-a64-spl32-lpddr3.bin`: 32bit build of a mainline based U-Boot SPL.
+Can be used for FEL booting. This version is for boards with the Allwinner A64
+SoC and LPDDR3 DRAM, like the SoPine or the Pinebook.
+- `sunxi-h5-spl32-ddr3.bin`: 32bit build of a mainline based U-Boot SPL.
+Can be used for FEL booting. This version is for boards with the Allwinner H5
+SoC and DDR3 DRAM, like the OrangePi PC2 or the NanoPi Neo 2.
+
+To FEL boot a board, connect your host computer to the OTG port of a board.
+On the Pine64 you need a special USB-A <-> USB-A cable connected to the upper
+USB port. Then use the sunxi-fel program from the sunxi-tools [1] repository:
+
+    $ sunxi-fel -v spl sunxi-a64-spl32-ddr3.bin
+
+After that you can load further firmware components into DRAM, if required.
+
+To rebuild those binaries, fetch the sunxi64-fel32 branch from
+[this U-Boot](https://github.com/apritzel/u-boot/commits/sunxi64-fel32)
+repository:
+
+    $ git checkout sunxi64-fel32
+    $ export CROSS_COMPILE=arm-linux-gnueabihf-
+    $ make sun50i-a64-ddr3-spl_defconfig
+    $ make
+
+The full U-Boot will probably fail to build, but you can pick up the SPL binary
+by just copying spl/sunxi-spl.bin. Alternative defconfigs provided are:
+- `sun50i-a64-ddr3-spl_defconfig`: A64 with DDR3 DRAM (Pine64, BananaPi M64)
+- `sun50i-a64-lpddr3-spl_defconfig`: A64 with LPDDR3 DRAM (Pine64 LTS, Pinebook)
+- `sun50i-h5-ddr3-spl_defconfig`: H5 with DDR3 DRAM (OrangePi PC2)