Using EMMC on OMAP4 devices

Using eMMC on OMAP4
The eMMC partition table is as shown below

Sector#   Size     Name 256    128K     xloader 512    256K     bootloader 2048      8M     boot 18432    512M     system 1067008    256M     cache 1591296    512M     userdata 2639872   2191M     media

We use fastboot to flash all the partitions above

First time flashing on eMMC
If there is no u-boot on your board's eMMC, you will have to boot using SD card. Copy u-boot.bin and MLO files to an SD card (boot partition) and then boot the target board from this external SD card using the following SYSBOOT switch settings to boot from external SD card: 01011101

For SDP4430 board: Switch S8-(1:8): OFF ON OFF ON ON ON OFF ON   For Blaze board: Switch S2-(1:8): OFF ON OFF ON ON ON OFF ON

Note: S8-(6:1) corresponds to SYSBOOT[5:0] in TRM. (ON=0, OFF=1)

Once you boot the board, start fastboot server on the target (OMAP4 board).

# fastboot

You should see a message Fastboot started

Now from the PC execute following commands to flash MLO and u-boot to eMMC ./fastboot oem format ./fastboot flash xloader ./MLO ./fastboot flash bootloader ./u-boot.bin

Now change the following SYSBOOT switch settings to boot out of EMMC: 11111101 whenever the board is restarted.

For SDP4430 board: Switch S8-(1:8): ON ON ON ON ON ON OFF ON   For Blaze board: Switch S2-(1:8): ON ON ON ON ON ON OFF ON

You can use the fastboot.sh script from the repo or use the one shown below to to flash all these partitions. Note the binary names used for each partition.

./fastboot flash xloader ./MLO ./fastboot flash bootloader ./u-boot.bin ./fastboot reboot-bootloader sleep 5 # < Note after running reboot-bootloader command you will see that the board reboots with the flashed u-boot > ./fastboot flash boot ./boot.img ./fastboot flash system ./system.img ./fastboot flash userdata ./data.img ./fastboot flash cache ./cache.img

Boot.img details
The boot.img is generated using umulti.sh script (also shown below)

./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

As you see in the line above, the kernel image used is zImage instead of uImage that we usually use.

TIP: If you have a uImage, you can create a zImage from it using the following command dd if=uImage bs=64 skip=1 of=zImage

The zImage is combined with ramdisk.img, which contains all the initial boot up programs (init, init.rc etc).

Opening and changing files in ramdisk.img for debugging
A ramdisk is basically a small filesystem containing the core files needed to initialize the system. It includes the critical init process, as well as init.rc, which is where you can set many system-wide properties. If you really want to know more about it, here is the documentation. Here's a list of files on a typical ramdisk: data default.prop dev env.txt init init.goldfish.rc init.omapzoom2.rc init.rc proc sbin\ sbin\adbd sbin\hotplug

Here are the steps to open, edit and create a new ramdisk.img

# cp ramdisk.img ramdisk.img.bkup # mkdir tmp && cd tmp
 * Copy the ramdisk.img to your UBuntu (Linux) machine
 * Back up ramdisk.img and Create a temporary folder, say tmp

# gunzip -c ../ramdisk.img | cpio -i Modify the contents of file in tmp folder eg. init.rc
 * Extract the ramdisk using the command below
 * Modify the contents of tmp folder. The contents of tmp folder will get into the ramdisk.img

# find. | cpio -o -H newc | gzip > ../ramdisk.img
 * Recreate the ramdisk.cpio with command:

Once the ramdisk.img is re-generated, you need to regenerate the boot.img using mkbootimg command shown above, and flash it for your init.rc changes to get reflected. Similarly, for updating the kernel you should regenerate boot.img with new zImage and flash it using fastboot command in earlier section.

TIP: If you want to just test your boot.img, without flashing you can use the command below

./fastboot boot ./boot.img

System.img details
System image is a sparsed ext4 loop mounted file system. To open (mount) system image use the commands below

./simg2img system.img system.img.raw mkdir tmp sudo mount -t ext4 -o loop system.img.raw tmp/

After this, all your system image files are part of tmp folder.

Make any changes you need in the tmp folder. To re-create the parsed system image (system.img.new) use the command below. This can be individually flashed using fastboot command

sudo ./make_ext4fs -s -l 512M -a system system.img.new tmp/ sudo umount tmp rm -rf tmp

Userdata.img details
This partition contains user-installed applications and data, including customization data

Again this is a sparsed ext4 loop mounted filesystem. To extract the sparesed image, use the command below

./simg2img userdata.img userdata.img.raw ./mkdir tmp sudo mount -t ext4 -o loop userdata.img.raw tmp/

Now you can make any changed in the tmp folder. To re-create a new userdata.img, use the command below to generate userdata.img.new, which can be flashed using fastboot.

# The command below is the original one - it does not work from GB onwards. So I've commented it out # and added a version that does work. I'm leaving the original behind for reference. # sudo ./make_ext4fs -s -l 512M -a userdata userdata.img.new tmp/ sudo ./make_ext4fs -s -l 512M -a data userdata.img.new tmp/

sudo umount tmp rm -rf tmp

Cache.img details
This partition can be used to store temporary data. It is currently an empty ext4 image.

Commands to create this image

mkdir tmp/ sudo ./make_ext4fs -s -l 256M -a cache cache.img tmp/

Frequently used Commands for eMMC
To remount system partition in R/W mode for OMAP4

adb remount                 - remounts the /system partition on the device read-write

To remount rootfs as R/W mode

mount -o rw,remount -t auto /dev/block/mmcblk0p1 /

To add busybox run the commands below

adb shell 'chmod 0755 /data/busybox/bin/* /data/busybox/sbin/*' adb shell '/data/busybox/bin/mount -oremount,rw /' adb shell '/data/busybox/bin/mount -oremount,rw /system' adb shell 'ln -s /data/busybox/bin /system/vendor/bin' adb shell 'ln -s /data/busybox/sbin /system/vendor/sbin'