Re: [U-Boot] using initrd with U-boot on the imx28evk

17 Sep 2012

      Dear Bill,
I'm CCing Fabio ... he might have some idea for you.
...
Marek,
 Yes, I checked the kernel and it is  enabled for ramdisk support in

Linux, gzip compression, and loop back block driver.  I did find some
other posts where some folks added the address of the ram drive.  So I
changed the kernel arguments from:
setenv bootargs console=ttyAM0,115200n8 debug root=/dev/ram rw ip=dhcp 
fec_mac= TO:
setenv bootargs console=ttyAM0,115200n8 debug root=/dev/ram rw
initrd=0x43000000,40K   ip=dhcp  fec_mac=
And now  the kernel output generates a additional error line from RAMDISK:
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RAMDISK: Couldn't find valid RAM disk image starting at 0. <<<<<<<< This
line now appears on the console
List of all partitions:
b300         3872256 mmcblk0 driver: mmcblk
   b301            1024 mmcblk0p1
0800          503808 sda driver: sd
   0801          503792 sda1
No filesystem could mount root, tried:  ext3 ext2 vfat msdos iso9660
Kernel panic - not syncing: VFS: Unable to mount root fs on
unknown-block(1,0)
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Is it something with the RAM disk format or the uboot tool mkimage
parameters?
Thanks,
Bill
On 9/12/2012 6:44 PM, Marek Vasut wrote:
...
Dear Bill,
...
I'm using U-boot version:  U-Boot 2012.07
Through googling, I've come across several variations of using a
ramdisk.  So I selected some things that looked good.  So basically, I
am building  a rootfs as a ramdisk by:
     dd if=/dev/zero of=./myinitrd.img bs=1M count=35
     mke2fs -m 1 ./myinitrd.img
     mkdir ./myinitrd
     mount -t ext2 ./myinitrd.img ./myinitrd -o loop
     cp -r rootfs/*  ./myinitrd/.
     umount ./myinitrd/
     gzip ./myinitrd.img
     rm -rf myinitrd
Then I use the u-boot tool to prepare it for use with u-boot by:
       u-boot-imx/tools/mkimage  -n 'MyRamDisk' -A arm -O linux -T
ramdisk -C none -d ./myinitrd.img.gz rootfs-initrd
I place both both my uImage and rootfs-initrd on a USB stick and insert
it into the imx28evk and enter u-boot command line.  I then do:
     usb start
     fatload usb 0 0x42000000 uimage
     fatload usb 0 0x43000000 rootfs-initrd
     setenv bootargs console=ttyAM0,115200n8 debug root=/dev/ram rw
ip=dhcp  fec_mac=
 bootm 0x42000000 0x43000000

u-boot then starts booting with:
## Booting kernel from Legacy Image at 42000000 ...
 Image Name:   Linux-2.6.35.3-571-gcca29a0-g45b
 Created:      2012-09-08  22:31:46 UTC
 Image Type:   ARM Linux Kernel Image (uncompressed)
 Data Size:    2582304 Bytes = 2.5 MiB
 Load Address: 40008000
 Entry Point:  40008000
 Verifying Checksum ... OK

## Loading init Ramdisk from Legacy Image at 43000000 ...
 Image Name:   MyRamDisk
 Created:      2012-09-12  20:51:35 UTC
 Image Type:   ARM Linux RAMDisk Image (uncompressed)
 Data Size:    37774 Bytes = 36.9 KiB
 Load Address: 00000000
 Entry Point:  00000000
 Verifying Checksum ... OK
 Loading Kernel Image ... OK

OK
Starting kernel ...
Uncompressing Linux... done, booting the kernel.
Linux version 2.6.35.3-571-gcca29a0-g45b53d0-dirty (blsousan@ubuntu)
(gcc version 4.4.4 (4.4.4_09.06.2010) ) #13 PREEMPT Sat Sep 8 14:06:34
PDT 2012
CPU: ARM926EJ-S [41069265] revision 5 (ARMv5TEJ), cr=00053177
CPU: VIVT data cache, VIVT instruction cache
Machine: Freescale MX28EVK board
....
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....
The kernel starts to boot, I get all the kernel output, and at the end
it does not find the rootfs.  I get:
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...
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List of all partitions:
b300         3872256 mmcblk0 driver: mmcblk
b301            1024 mmcblk0p1

0800          503808 sda driver: sd
0801          503792 sda1

No filesystem could mount root, tried:  ext3 ext2 vfat msdos iso9660
Kernel panic - not syncing: VFS: Unable to mount root fs on
unknown-block(1,0)
Backtrace:
I not sure how the kernel knows where the ramdisk lives in memory (
0x43000000) where the the uboot put it ?
Thanks,
Bill
On 9/12/2012 5:29 PM, Marek Vasut wrote:
...
Dear Bill,
...
Has anyone used U-boot on the imx28evk with initrd to setup a small
rootfs in RAM?  I need the ability to do have a small temp rootfs to
assist in mounting a full rootfs from a USB for field upgrade
purposes.
Yes, it's a linux thingie though. What's the problem? What version of
uboot do you use?
Some ancient kernel you have ... did you enable ramdisk support in Linux?
And gzip compression for it ? And loop back block driver ?
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Thanks,
Bill
Best regards,
Marek Vasut
Best regards,
Marek Vasut