mmc rootfs not detected

I'm using a standard build kernel from

http://code.google.com/p/mini2440/wiki/OpenEmbedded

The kernel is booting fine and inside a qemu test it is detecting the SD
card image fine. But when i try to use an SD card on a real board the
partition isn't recognised so it kernel panics.

VFS: Cannot open root device "mmcblk0p1" or unknown-block(2,0)
Please append a correct "root=" boot option; here are the available
partitions:
1f00     256  mtdblock0 (driver?)      
1f01     128  mtdblock1 (driver?)
1f02    5120  mtdblock2 (driver?)
1f03  125568  mtdblock3 (driver?)
 
Kernel panic - not syncing: VFS: Unable to mount root fs on
unknown-block(2,0)

I would expect to see the mmc partitions listed here as well. Further up
the output from the kernel i have this message

sdhci: Secure Digital Host Controller Interface driver
sdhci: Copyright(c) Pierre Ossman              
s3c-sdi s3c2440-sdi: powered down.        
s3c-sdi s3c2440-sdi: mmc0 - using pio, sw SDIO IRQ

But its not picking up the card at all. In qemu (both are running exactly
the same kernels, so i know that SD support and ext3 are in there) i get
this

mmc0: new SD card at address 4567
mmcblk0: mmc0:4567 QEMU! 256 MiB 
 mmcblk0:
 p1

But no such luck on the real board. Anyone else had this problem?

I should add that my kernel command line is

console=ttySAC0,115200 noinitrd init=/sbin/init mini2440=1tb
root=/dev/mmcblk0p1 rootfs=ext3

I'm aware that i shouldn't need the rootfs parameter but it also shouldn't
hurt (tried with/without anyway)

I can also add that if i run 

> mmcinit
> ext2ls mmc 0:1

I get to see all the files, so i know that SD card is inserted and the slot
is working fine! So now i'm really stuck. I can't think of anything to
persuade the kernel to pick up the card.

OK so to continue the conversation with myself it turns out its the type of
card.

I tried a 2GB kingston a 1GB corsair both of which didn't work. Next 1
tried a 256MB kingston and that worked fine, so i'm guessing there's
something up with using SDHC cards? I thought i'd read that other people
have used these successfully? If so could someone point out what
modifications i need to make because i'd really like the extra space.

Andrew,

A long shot . . . from my experience getting SD cards working with FatFS on
the AVR ATmega32 there was quite a bit of traffic on:

www.avrfreaks.net

about 2GB Kingston cards.  They didn't appear to work (initialise) the same
way as many other cards.

You could go to that site and drop <Kingston> in search.

Good luck.

I just noticed that if I use a usb card reader I instantly get sda working,
but if I use the card reader on the board I get nothing.

add >> rootwait << to your kernel params.

Hi Andrew Gatt, 
I have the same issue as yours. Looks like 2 years don't change stuff much.
Were you able to resolve the issue. 

Regards, 
Yogik