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

[Marek Vasut <marex@denx.de>]

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:
> 
> ...
> ...
> ...
> 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)
> ...
> ...
> ...
> 
> 
> 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 at 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
> >> ....
> >> ....
> >> ....
> >> 
> >> The kernel starts to boot, I get all the kernel output, and at the end
> >> it does not find the rootfs.  I get:
> >> 
> >> ...
> >> ...
> >> ...
> >> 
> >> 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 ?
> > 
> >>>> Thanks,
> >>>> Bill
> >>> 
> >>> Best regards,
> >>> Marek Vasut
> > 
> > Best regards,
> > Marek Vasut