Android eMMC Booting

Android eMMC Booting

 

Contents

 [hide]

• 1 eMMC binaries
  • 1.1 Creating the GPT table
  • 1.2 Modifying .IMG Files
  • 1.3 TI Android build setup

[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

1. Connect a USB cable to the OTG port on your platform
2. Boot your platform up with a stock u-boot and MLO
3. 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/
 # 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/
 %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.