🛠 Boot microSD/eMMC et chaîne de démarrage Amlogic

Objectives

Understand and master the proprietary Amlogic boot chain of the ODROID-C2 (signed BL1, FIP, U-Boot), migrate the system from a microSD card to an eMMC module (much faster and more reliable: HS200 bus versus SDR50/SDR100 limited in mainline), and know how to reject a fallback media.

Hardware

• ODROID-C2, microSD + Hardkernel eMMC module (8 to 64 GB)
• Card reader and microSD-to-eMMC adapter (or the card itself)
• Serial console uart_AO 115200 8N1 to monitor the boot
• bl1.bin.hardkernel (hardkernel/u-boot repo, odroidc2-v2015.01 branch) and u-boot.bin.gxbb signed via LibreELEC amlogic-boot-fip (build-fip.sh odroid-c2)

Complete code

# 1) Copie integrale du systeme SD -> eMMC (depuis la carte qui boote sur SD)
sudo dd if=/dev/mmcblk0 of=/dev/mmcblk1 bs=16M status=progress conv=fsync
# (mmcblk0 = SD, mmcblk1 = eMMC — verifier avec lsblk avant !)

# 2) Refuser la zone de boot Amlogic sur le nouveau media si besoin :
#    BL1 sur les 442 premiers octets, puis secteur 1, U-Boot signe au secteur 97
DEV=/dev/mmcblk1; BL1=bl1.bin.hardkernel
sudo dd if=$BL1 of=$DEV conv=fsync bs=1 count=442
sudo dd if=$BL1 of=$DEV conv=fsync bs=512 skip=1 seek=1
sudo dd if=u-boot.bin.gxbb of=$DEV conv=fsync bs=512 seek=97
sync

# 3) Tete-etre headless : editer boot.ini (images vendor) —
#    setenv nographics "1" libere ~300 Mo de RAM

# 4) Redemarrer sur l'eMMC puis mesurer le gain :
sudo dd if=/dev/zero of=test.bin bs=1M count=256 oflag=direct conv=fdatasync && rm test.bin

Expected verification

By removing the microSD card, the board boots alone on the eMMC (visible on the serial console: BL1/FIP/U-Boot then kernel). The dd test goes from a few MB/s on a cheap microSD to 100+ MB/s on an HS200 eMMC. The Amlogic boot ROM always reads BL1 first: without the refused boot area, no media boots.

Common errors

• Inverting mmcblk0/mmcblk1 and dd in one direction or the other: destruction of the source system. Always check lsblk and disk sizes.
• Believing in a 100% free chain: BL1/BL3x are non-redistributable blobs, even mainline U-Boot must be signed (amlogic-boot-fip).
• Forgetting sync before unmounting: corrupted system on eMMC.
• Using old vendor images Ubuntu 16.04/Android 5.1 (kernel 3.14) exposed on the network: old vulnerabilities; prefer Armbian/DietPi/ALARM.
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