Espressobin - building U-Boot

Continuing in the topic of the previous post - building the Kernel - I look into how Armbian builds U-Boot for the Espressobin.
There is some info on building U-Boot on the wiki but even though I tried to follow it to the letter, the U-Boot I build would never boot. Yet the U-Boot binaries build by Armbian work OK. Also note that there are several board revisions, so you certainly need sufficient new U-Boot or you can run into funny issues.

So, untangling the Armbian build scripts further (see the previous post for some context), let's see how the U-Boot is built:

• the relevant sources are fetched in lib/main.sh and they are, at time of this this writing:
• marvel-tools: https://github.com/MarvellEmbeddedProcessors/A3700-utils-marvell, branch A3700_utils-armada-18.12
• marvell-ddr: https://github.com/MarvellEmbeddedProcessors/mv-ddr-marvell.git, branch mv_ddr-armada-18.12
• ATF: https://github.com/MarvellEmbeddedProcessors/atf-marvell, branch atf-v1.5-armada-18.12
• U-Boot: https://github.com/MarvellEmbeddedProcessors/u-boot-marvell.git, branch u-boot-2018.03-armada-18.12

First the ATF's bl32.bin is built by compile_atf:

• change into the ATF directory
• ATF_TARGET_MAP (which is defined in config/sources/mvebu64.conf) is parsed - split by ; into three parts:
• target_make: DEBUG=1 USE_COHERENT_MEM=0 LOG_LEVEL=20 SECURE=0 CLOCKSPRESET=CPU_800_DDR_800 DDR_TOPOLOGY=2 BOOTDEV=SPINOR PARTNUM=0 PLAT=a3700
• target_patchdir: (empty)
• target_files: build/a3700/debug/bl31.bin
• advanced_patch atf atf-mvebu64 espressobin $target_patchdir next mvebu64-espressobin-next, applies patches from:
• patch/atf/atf-mvebu64/target_
• patch/atf/atf-mvebu64/board_espressobin
• patch/atf/atf-mvebu64/branch_next
• patch/atf/atf-mvebu64
• none of the directories exist, so no patches are applied for the Espressobin
•  make $target_make CROSS_COMPILE="$ATF_COMPILER"
• ATF_COMPILER='aarch64-linux-gnu-' (see config/sources/mvebu64.conf)
• atf_custom_postprocess from config/sources/mvebu64.conf is called
• packages/blobs/espressobin/DDR_TOPOLOGY_*.txt is copied into cache/sources/marvell-tools/tim/ddr/ (that is in the marvell-tools - or A3700-utils-marvell - repo clone)
• copy all $target_files - which, for the Espressobin, is just 1 file: build/a3700/debug/bl31.bin - into .tmp/atf-${LINUXFAMILY}-${BOARD}-${BRANCH} ... where it's magicaly found by compile_uboot, yay!

Then U-Boot is built by compile_uboot. It does:

• change into U-Boot directory
• UBOOT_TARGET_MAP is read (defined in config/sources/mvebu64.conf), and for each line the loop body is called:
• for the Espressobin there is only one line in
  UBOOT_TARGET_MAP and so the loop it executed just once with target = "DEVICE_TREE=armada-3720-espressobin ;;flash-image-*.bin"
• target is split by ; into:
• target_make: armada-3720-espressobin (luckily the trailing space seems to be dropped)
• target_patchdir: (empty)
• target_files: flash-image-*.bin
• patches are applied by the advanced_patch machinery: advanced_patch "u-boot" "$BOOTPATCHDIR" "$BOARD" "$target_patchdir" "$BRANCH" "${LINUXFAMILY}-${BOARD}-${BRANCH}"
• BOOTPATCHDIR is u-boot-mvebu64 (lib/configuration.sh)
• so this becomes: advanced_patch u-boot u-boot-mvebu64 espressobin "" next mvebu64-espressobin-next
• patches are applies searched for in:
• patch/u-boot/u-boot-mvebu64/target_
• patch/u-boot/u-boot-mvebu64/board_espressobin
• patch/u-boot/u-boot-mvebu64/branch_next
• patch/u-boot/u-boot-mvebu64
• only patch/u-boot/u-boot-mvebu64 exists and contains currently 1 patch
• cp -Rv $atftempdir/*.bin .
• this "recovers" the files built in the ATF step (bl31.bin) and copies them to the u-boot src dir
• make U-Boot config: make $BOOTCONFIG CROSS_COMPILE="$CCACHE $UBOOT_COMPILER"
• UBOOT_COMPILER="aarch64-linux-gnu-" (lib/configuration.sh)
• BOOTCONFIG="mvebu_espressobin-88f3720_defconfig"
• patch U-Boot config
• set LOCALVERSION to "-armbian"
• setU-Boot env to be stored on a mmc on ext4 in /boot/boot.env
• build U-Boot: make $target_make $CTHREADS CROSS_COMPILE="$CCACHE $UBOOT_COMPILER"
• target_make: DEVICE_TREE=armada-3720-espressobin
• UBOOT_COMPILER="aarch64-linux-gnu-" (lib/configuration.sh)
• uboot_custom_postprocess from config/sources/mvebu64.conf is called - this does the wrapping in ATF
• change into the ATF source directory
• builds for all combinations of:
• clocks=( 600_600 800_800 1000_800 1200_750 )
• topology=( 512m_1cs_0 512m_2cs_0 1g_2cs_2 1g_1cs_4 2g_2cs_2 1g_1cs_5 2g_2cs_6 )
• *cs_5 or *cs_6 means DDR4, others are DDR3 (see here)
• if you build just for one revision, then you need to pick one of the clocks and topology values, for example for the Espressobin V5_0_1 with 2GiB, 2 chips, the values seem to be:
• clock: 1000_800
• topology: 2g_2cs_2
• DDR_TOPOLOGY is set to the suffix after the last _ in topology (e.g. "2")
• CLOCKSPRESET is set to "CPU_${i%_*}_DDR_${i##*_}", e.g. CPU_1000_DDR_800
• the actual ATF binaries are built: make MV_DDR_PATH=$SRC/cache/sources/marvell-ddr CROSS_COMPILE=$ATF1 DEBUG=1 USE_COHERENT_MEM=0 LOG_LEVEL=20 SECURE=0 CLOCKSPRESET=$CLOCKSPRESET DDR_TOPOLOGY=$DDR_TOPOLOGY BOOTDEV=SPINOR PARTNUM=0 PLAT=a3700 all fip BL33=$BL33 WTP=$SRC/cache/sources/marvell-tools $CTHREADS CROSS_CM3=$ATF2
• ATF1=$toolchain/$ATF_COMPILER (set in atf_custom_postprocess)
• ATF_COMPILER='aarch64-linux-gnu-' (in config/sources/mvebu64.conf)
• ATF2=arm-linux-gnueabi- (in config/sources/mvebu64.conf)
• BL33=$ubootdir"/u-boot.bin" (set in atf_custom_postprocess)
• the resulting files are produced in build/a3700/debug

Whoa... not easy, and the build scripts don't make understanding the flow any easier.