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Revision as of 16:16, 10 February 2011

Boot from SD/MMC

The Following Procedure explains how to boot a Kernel Image and Root File system from a SD/MMC card. Thus a NAND flash is no more a mandatory component to have on our Electrum100 boards. Boot from SD/MMC card gives a wide range of options for the user including portability, larger memory etc,. In our test bed, we didn't see a considerable change in the speed of the board, thus speed is not a big concern when booting from SD/MMC given the advantages it provides.

Note: As EXT2 File system is used, there is no Journalism. So its recommended to use standard commands every time you Reboot or Shutdown.

shutdown -h now   to Shutdown
shutdown -r now   to Restart

To boot Kernel and Rootfs from SD/MMC card (Without NAND)

1) Download u-boot-2010.03 from http://wiki.micromint.com/index.php/Electrum_Documentation

2) Build u-boot-2010.03 source or download the binary.

$make bootloader

3) Update the Boot strapper and Boot-loader into Electrum100 using SAM-BA application

4) Execute the command:

Electrum> mmc list 
Electrum> mmc rescan 0

5) Now copy the Kernel Image and rootfs into SD card (Refer the section: Creating a Bootable filesystem on SD card).

6) Check the card using "mmc rescan 0" command

7) change the boot args to load root file system from SD card.

setenv bootargs console=ttyS0,115200 root=/dev/mmcblk0p1 rw ip=192.168.1.231:192.168.1.249::255.255.255.0::eth0:none

8) To load the Kernel from EXT2 change the boot commands

Electrum> setenv bootcmd mmcinfo\; ext2load mmc 0:1 0x22000000 uImage-2.6.33.5\; bootm
Electrum> saveenv
Electrum> reset

Creating a Bootable Filesystem on SD card

1) The first step is to make a bootable file system on the SD card. Insert the card into the slot of a running plug. Enter the following commands:

$ fdisk /dev/mmcblk0
press "o"  / create a new partition table
press "n"  / create a new partition
press "p"  / it's a primary partition
press "1"  / partition #1
press enter / default first cylinder
press enter / default last cylinder
press "a"  / set the boot flag
press "1" / ... for partition #1
press "w" / save changes

Command (m for help): o
Building a new DOS disklabel with disk identifier 0xc57e78f0.
Changes will remain in memory only, until you decide to write them.
After that, of course, the previous content won't be recoverable.

Command (m for help): n
Command action
   e   extended
   p   primary partition (1-4)
p
Partition number (1-4): 1
First cylinder (1-1203, default 1): 
Using default value 1
Last cylinder, +cylinders or +size{K,M,G} (1-1203, default 1203): 
Using default value 1203

Command (m for help): a
Partition number (1-4): 1

Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.
Syncing disks.
	
$ mkfs -t ext2  /dev/mmcblk0p1
$ mkdir /mnt/sdcard
$ mount /dev/mmcblk0p1 /mnt/sdcard
$ df

2) Now copy your existing nand file system onto the sd card. This may take 5-10 minutes.

root#: cp -r /rootfs/* /mnt/sdcard

3) The SD card should now mirror your internal nand flash, which you can confirm with df -h, etc.

Filesystem           1K-blocks      Used Available Use% Mounted on
rootfs                  519168    185612    333556  36% /
tmpfs                   257816         0    257816   0% /lib/init/rw
varrun                  257816       260    257556   1% /var/run
varlock                 257816         0    257816   0% /var/lock
udev                    257816        12    257804   1% /dev
tmpfs                   257816         0    257816   0% /dev/shm
tmpfs                   257816     21824    235992   9% /var/cache/apt
/dev/mmcblk0p1         7707056    516216   6799340   8% /mnt/sdcard

your SD card now has a bootable system. The next step is to boot it.

Booting from the SD Card

You need to interact with u-boot now. You must do this from a program talking to the usb-serial port, not from an ssh shell (duh).

>shutdown -r now

When u-boot appears, stop it by typing ENTER a few times, to stop it from booting automatically.

Electrum>> printenv bootargs
bootargs console=ttyS0,115200 root=/dev/nfs rw ip=192.168.1.231:192.168.1.249::255.255.255.0::
eth0: nfsroot=192.168.1.249:/media/disk/rootfs

This is the line that you'll need to change. Change it to

Electrum>> setenv bootargs console=ttyS0,115200 root=/dev/mmcblk0p1 rw ip=192.168.1.231:192.168.1.249::255.255.255.0::
eth0:none
Electrum>> printenv bootargs (if you like, just to confirm that you did it right)
Electrum>> saveenv
Electrum>> boot