Android eMMC Booting

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

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//system.img
• cache.img -->
• userdata.img --> $mydroid/out/target/product//userdata.img

All these partitions can be flashed with the given binary using fastboot.

fastboot flash  

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

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
 
 %./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  
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/
 %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

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.