Putting Linux on mini2440 with jffs2 filesystem
The [previous post]({% post_url 2015-04-05-linux-mini2440 %}) showed how to put Linux on the mini2440.
If you log in at the login prompt by entering the username root, you would be taken to /root. If you try writing to the filesystem,
# touch test
and you restart the device
# reboot
you will find that the file is not saved. To be able to write to the flash, we can place a jffs2 filesystem on the mini2440.
Building the kernel and root file system
Using the same version of buildroot from the [previous post]({% post_url 2015-04-05-linux-mini2440 %}), I did make menuconfig.
Deselect initial RAM filesystem linked into linux kernel and deselect cpio the root filesystem (for use as an initial RAM filesystem)
I also selected jffs2 root filesystem and for Flash Type, I selected NAND flash with 2kB Page and 128 kB erasesize
Then…
make
Conceptually,
You want to put U-Boot, a bootloader, into NAND flash, which will then load your linux kernel, which would in turn load your root filesystem.
You can use the U-Boot bootloader if it is already on the mini2440’s NAND flash.
Transferring uImage into NAND flash
Find the address of the kernel partition:
MINI2440 # mtdparts
device nand0 <mini2440-nand>, # parts = 4
#: name size offset mask_flags
0: u-boot 0x00040000 0x00000000 0
1: u-boot_env 0x00020000 0x00040000 0
2: kernel 0x00500000 0x00060000 0
3: rootfs 0x0faa0000 0x00560000 0
active partition: nand0,0 - (u-boot) 0x00040000 @ 0x00000000
defaults:
mtdids : nand0=mini2440-nand
mtdparts: <NULL>
Erase the kernel partition:
MINI2440# nand erase 60000 500000
Download uImage from Linux PC over LAN into RAM, at 0x32000000 again. First place uImage into /tftpboot (Google how to set up tftp).
MINI2440# tftp 32000000 uImage
Copy uImage from ram into NAND
MINI2440# nand write.e 32000000 60000 <size-of-uImage-in-hex>
Set the boot command to load kernel image from NAND flash.
MINI2440# setenv bootcmd 'nboot.e kernel;bootm'
MINI2440# saveenv
Transferring rootfs.jffs2 into NAND flash
Copy rootfs.jffs2 from buildroot-2015.02/output/images/ into /tftpboot/.
Erase the rootfs partition:
MINI2440# nand erase rootfs
Download rootfs.jffs2 from Linux PC over LAN into RAM, at 0x32000000 again.
MINI2440# tftp 32000000 rootfs.jffs2
Copy uImage from ram into NAND
MINI2440# nand write.e 32000000 560000 <size-of-rootfs.jffs2-in-hex>
Set the boot command to load kernel image from NAND flash.
MINI2440# setenv bootcmd 'nboot.e kernel;bootm'
MINI2440# setenv bootargs 'root=/dev/mtdblock3 rootfstype=jffs2 console=ttySAC0,115200'
MINI2440# saveenv
Power cycle the mini2440.
Full U-Boot environment for reference
MINI2440 # printenv
bootargs=root=/dev/mtdblock3 rootfstype=jffs2 console=ttySAC0,115200
bootdelay=3
baudrate=115200
ethaddr=08:08:11:18:12:27
usbtty=cdc_acm
mini2440=mini2440=0tb
bootargs_base=console=ttySAC0,115200 noinitrd
bootargs_init=init=/sbin/init
root_nand=root=/dev/mtdblock3 rootfstype=jffs2
root_mmc=root=/dev/mmcblk0p2 rootdelay=2
root_nfs=/mnt/nfs
set_root_nfs=setenv root_nfs root=/dev/nfs rw nfsroot=${serverip}:${root_nfs}
ifconfig_static=run setenv ifconfig ip=${ipaddr}:${serverip}::${netmask}:mini2440:eth0
ifconfig_dhcp=run setenv ifconfig ip=dhcp
ifconfig=ip=dhcp
set_bootargs_mmc=setenv bootargs ${bootargs_base} ${bootargs_init} ${mini2440} ${root_mmc}
set_bootargs_nand=setenv bootargs ${bootargs_base} ${bootargs_init} ${mini2440} ${root_nand}
set_bootargs_nfs=run set_root_nfs; setenv bootargs ${bootargs_base} ${bootargs_init} ${mini2440} ${root_nfs} ${ifconfig}
mtdids=nand0=mini2440-nand
mtdparts=mtdparts=mini2440-nand:0x00040000(u-boot),0x00020000(u-boot_env),0x00500000(kernel),0x0faa0000(rootfs)
bootcmd=nboot.e kernel;bootm
filesize=51A630
fileaddr=32000000
netmask=255.255.255.0
ipaddr=192.168.1.60
serverip=192.168.1.50
partition=nand0,0
mtddevnum=0
mtddevname=u-boot