Android eMMC Booting
Android eMMC Booting
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[edit]eMMC binaries
This is the efi partition table as exists on the emmc
Sector# Size Name 256 128K xloader 512 256K bootloader 2048 8M recovery 18432 8M boot 34816 512M system 1083392 256M cache 1607680 512M userdata 2656256 2183M media
[edit]Creating the GPT table
- On Target
- Connect a USB cable to the OTG port on your platform
- Boot your platform up with a stock u-boot and MLO
- Once you platform is booted you will see the following:
Fastboot entered...
- On Host Machine
locate fastboot in you android filesystem
cd $mydroid/out/host/linux-x86/bin/fastboot
Search for fastboot devices
fastboot devices
Create GPT table on eMMC/SD card
fastboot oem format
From the android build these are the binaries that go into each partition:
Sector# Size Name Binary 256 128K xloader MLO 512 256K bootloader u-boot.bin 2048 8M recovery recovery.img 18432 8M boot boot.img 34816 512M system system.img 1083392 256M cache cache.img 1607680 512M userdata userdata.img 2656256 2183M media none
- File locations
- MLO --> x-loader/MLO
- u-boot --> u-boot/u-boot.bin
- boot.img --> need to create using zImage + ramdisk.img
- recovery.img ---> need to create using zImage + ramdisk-recovery.img
- system.img --> $mydroid/out/target/product/<platform>/system.img
- cache.img -->
- userdata.img --> $mydroid/out/target/product/<platform>/userdata.img
All these partitions can be flashed with the given binary using fastboot.
fastboot flash <name> <binary>
Example flashing of all partitions
fastboot flash xloader MLO fastboot flash bootloader u-boot.bin fastboot flash recovery recovery.img fastboot flash boot boot.img fastboot flash system system.img fastboot flash cache cache.img fastboot flash userdata userdata.img
[edit]Modifying .IMG Files
Typically when you want to modify any of the partitions, you would need to unzip-modify-rezip and then fastboot flash.
Following section talks about how to do that for each partition
BOOT.IMG
boot.img = zImage + ramdisk.img zImage = kernel image ramdisk.img = out/target/product/blaze/root/ %./out/host/linux-x86/bin/mkbootimg --kernel zImage --ramdisk ramdisk.img --base 0x80000000 --cmdline "console=ttyO2,115200n8 mem=456M@0x80000000 mem=512M@0xA0000000 init=/init vram=10M omapfb.vram=0:4M androidboot.console=ttyO2" --board omap4 -o boot.img.new Output: boot.img.new **Note: bootarg is passed to kernel via --cmdline option above
To "just" boot boot.img (before flashing) you can use:
%fastboot boot boot.img
RAMDISK.IMG
%mkdir root %cd root %gunzip -c ../ramdisk.img | cpio -i <make changes to root/ contents...> %./out/host/linux-x86/bin/mkbootfs root/ | ./out/host/linux-x86/bin/minigzip >ramdisk.img.new #output: ramdisk.img.new ** Note: any init.rc changes will need to use this method
RECOVERY.IMG
Is just like boot.img. recovery.img = zImage + ramdisk-recovery.img *Follow the same steps as boot.img for packing/unpacking
SYSTEM.IMG
#uncompress %./out/host/linux-x86/bin/simg2img system.img system.img.raw #mount to directory mnt-point/ %mkdir mnt-point %sudo mount -t ext4 -o loop system.img.raw mnt-point/ #modify any .so or apk in the mnt-point/ directory #rezip %sudo out/host/linux-x86/bin/make_ext4fs -s -l 512M -a system system.img.new mnt-point/ %sudo umount mnt-point/ Output: system.img.new
Instead of having to reflash the whole big system.img, one can selective update any binary in /system folder on running target
%adb remount %adb push <local> <remote> Eg: %adb remount %adb push out/target/product/blaze/obj/lib/overlay.omap4.so /system/lib/hw/overlay.omap4.so %adb sync
USERDATA.IMG
#uncompress %./out/host/linux-x86/bin/simg2img userdata.img userdata.img.raw #mount to directory mnt-point/ %mkdir mnt-point %sudo mount -t ext4 -o loop userdata.img.raw mnt-point/ #modify any .so or apk in the mnt-point/ directory #rezip #%sudo ./out/host/linux-x86/bin/make_ext4fs -s -l 512M -a userdata userdata.img.new mnt-point/ # Above command won't work on GB/HC. For GB/HC, please use the following updated command %sudo ./out/host/linux-x86/bin/make_ext4fs -s -l 512M -a data userdata.img.new mnt-point/ %sudo umount mnt-point/ Output: userdata.img.new
CACHE.IMG
#This is empty ext4 fs image %mkdir mnt-point/ %sudo ./make_ext4fs -s -l 256M -a cache cache.img mnt-point/ Output: cache.img
[edit]TI Android build setup
Copy kernel zImage, u-boot.bin and MLO for your board in folder device/ti/blaze/boot/.
Rename as:
%mv MLO MLO_es2.2_emu or %mv MLO MLO_es2.2_gp (based on your board being GP or EMU)
Next start standard android build and all img files are generated in:
out/target/product/blaze/*.img
A script is introduced in TI Android release to make this flashing process easier: device/ti/blaze/boot/fastboot.sh
Usage: cd device/ti/blaze/boot/ %fastboot.sh --emu or %fastboot.sh --gp
Running this script will flash whole android system on your board.