Kernel panic: VFS: Unable to mount root fs on unknown-block(1,0)

Hi Guys,

I am having problem loading the kernel from sdcard.

My boot sequence is 
1) spi bootloader(resides in spi flash)
2) fat16 file system (resides in spi flash)
3) zimage (resides on sd card)
3) ramdisk (resides on sd card)
3) kernel_bootstrap (resides on sd card)

The board boots from spi flash which in turn loads fat16 file system. It copies linux kernel @0x04000000, ramdisk @0x01000000, kernel_bootstrap @0x00001000. Then it executes kernel_bootstrap.

My board setup is sdram => 64MB, split into 2 banks
//bank 0 start at 0x00000000, length 0x02000000, 
//bank 1 start at 0x04000000, length 0x02000000, 

There is no onboard flash except for serial flash used to load the bootloader.

In my kernel bootstrap code i specify atags list for kernel. 
                .word   4
                .word   ATAG_INITRD2    @ second rev, physical mapped initrd 
                .word   0x01000000      @ start in second physical page
//                .word   0x01000000      @ start in second physical page
initrd_size:    .word   0x00000000      @ filled in by loader!


What is causing this error. Can some one please share some pointers.

I have added kernel log messages.
-------------------------------------------------------------------------
Uncompressing Linux.................................
.................................................. done, booting the kernel.
Linux version 2.6.8.1 (pritam@pritam-desktop) (gcc version 3.4.3) #1 Fri Dec 3 15:19:39 WST 2010
CPU: ARM920Tid(wb) [41129200] revision 0 (ARMv4T)
CPU: D VIVT write-back cache
CPU: I cache: 16384 bytes, associativity 64, 32 byte lines, 8 sets
CPU: D cache: 16384 bytes, associativity 64, 32 byte lines, 8 sets
Machine: edb9307
Memory policy: ECC disabled, Data cache writeback
        bank 0 start at 0x00000000, length 0x02000000, mapped to 0xc0000000
        bank 1 start at 0x04000000, length 0x02000000, mapped to 0xc2000000
On node 0 totalpages: 16384
  DMA zone: 16384 pages, LIFO batch:4
  Normal zone: 0 pages, LIFO batch:1
  HighMem zone: 0 pages, LIFO batch:1
Built 1 zonelists
Kernel command line: root=/dev/ram console=ttyAM debug
Relocating machine vectors to 0xffff0000
PID hash table entries: 512 (order 9: 4096 bytes)
Console: colour dummy device 80x30
Dentry cache hash table entries: 16384 (order: 4, 65536 bytes)
Inode-cache hash table entries: 8192 (order: 3, 32768 bytes)
Memory: 32MB 32MB = 64MB total
Memory: 62016KB available (1980K code, 548K data, 232K init)
Calibrating delay loop... 7.27 BogoMIPS
Mount-cache hash table entries: 512 (order: 0, 4096 bytes)
CPU: Testing write buffer coherency: ok
NET: Registered protocol family 16
SCSI subsystem initialized
usbcore: registered new driver usbfs
usbcore: registered new driver hub
Bluetooth: Core ver 2.6
NET: Registered protocol family 31
Bluetooth: HCI device and connection manager initialized
Bluetooth: HCI socket layer initialized
fb0: EP93xx frame buffer at 320x240x16
NetWinder Floating Point Emulator V0.97 (double precision)
JFFS version 1.0, (C) 1999, 2000  Axis Communications AB
JFFS2 version 2.2. (C) 2001-2003 Red Hat, Inc.
Console: switching to colour frame buffer device 40x30
ttyAM0 at MMIO 0x808c0000 (irq = 52) is a EP93XX
ttyAM1 at MMIO 0x808d0000 (irq = 54) is a EP93XX
ttyAM2 at MMIO 0x808e0000 (irq = 55) is a EP93XX
RAMDISK driver initialized: 16 RAM disks of 32768K size 1024 blocksize
loop: loaded (max 8 devices)
Using anticipatory io scheduler
CFI: Found no edb93xxflash0 device at location zero
edb93xxflash: probe of edb93xxflash0 failed with error -6
ep93xxusb ep93xxusb0: new USB bus registered, assigned bus number 1
hub 1-0:1.0: USB hub found
hub 1-0:1.0: 3 ports detected
usbcore: registered new driver audio
drivers/usb/class/audio.c: v1.0.0:USB Audio Class driver
Initializing USB Mass Storage driver...
usbcore: registered new driver usb-storage
USB Mass Storage support registered.
usbcore: registered new driver usbhid
drivers/usb/input/hid-core.c: v2.0:USB HID core driver
usbcore: registered new driver xpad
drivers/usb/input/xpad.c: X-Box pad driver:v0.0.5
usbcore: registered new driver dabusb
drivers/usb/media/dabusb.c: v1.54:DAB-USB Interface Driver for Linux (c)1999
usbcore: registered new driver usbnet
dummy_hcd hc0: USB Host+Gadget Emulator, driver 14 Mar 2004
dummy_hcd hc0: new USB bus registered, assigned bus number 2
hub 2-0:1.0: USB hub found
hub 2-0:1.0: 1 port detected
mice: PS/2 mouse device common for all mice
ts: Compaq touchscreen protocol output
Bluetooth: HCI USB driver ver 2.7
usbcore: registered new driver hci_usb
NET: Registered protocol family 2
IP: routing cache hash table of 512 buckets, 4Kbytes
TCP: Hash tables configured (established 4096 bind 8192)
NET: Registered protocol family 1
NET: Registered protocol family 17
JFFS: Trying to mount a non-mtd device.
Kernel panic: VFS: Unable to mount root fs on unknown-block(1,0)
-------------------------------------------------------------------------


Thanks
Tama