[U-Boot] u-boot preventing access to NAND chip on imx28evk board

[Bill <bsousan@techsi.com>]

All,

     I'm needing to access the NAND chip on the imx28evk board with the 
Linux (Freescale Kernel - FSL).  I've compiled a recent version of the 
mainstream u-boot with the NAND switches and U-boot works fine.  The 
U-boot also allows me access to the NAND chip and also boots the FSL 
kernel just fine.  However, once the kernel is running, it can not "see" 
the /dev/mtdX devices.

     However, if I boot the *same* kernel directly (no U-boot - and 
attach boot-stream to kernel) the FSL kernel works fine and can gets the 
/dev/mtdX etc devices.  I tracked this down to a couple of differences 
that are output during the kernel booting process.  I also can replicate 
this problem with no NAND chip in the socket. I can do this by using the 
script that comes with the imx28evk that is used for formatting the 
SDCard for booting.  The mk_mx28_sd script writes the uboot, kernel, and 
rootfs to an SDcard depending on the parameters.  So if I write the 
uboot to the card and boot the imx28 from uboot and network boot uImage 
I get the error.  If I write the kernel to the card and boot the imx28 
with it I get no error (Using the same kernel).  Here are the steps

1.  Setup card for kernel boot
- run mk_mx28_sd  -b /dev/sdb  (only writes kernel with bootstream on card)
- place card in imx28 and boot it
- the kernel (while booting) outputs these lines:
...
...
i.MX GPMI NFC
NFC: Version 1, 8-chip GPMI and BCH
Boot ROM: Version 1, Single-chip boot area, block mark swapping 
supported Scanning for NAND Flash chips...
No NAND device found.
gpmi-nfc gpmi-nfc.0: Chip scan failed
...
...


2.  Setup card for uboot
-setup your host ubuntu so uboot can tftp your kernel -use *same* kernel 
from #1 (but use uImage) -run mk_mx28_sd -u -b /dev/sdb (only writes 
uboot with bootstream on card) -place card in imx28 and boot it -you may 
have to edit uboot parms to get your uImage from your host -Allow kernel 
to boot, it will output these lines:

...
i.MX GPMI NFC
NFC: Version 1, 8-chip GPMI and BCH
gpmi-nfc: probe of gpmi-nfc.0 failed with error 1 ...
...



So maybe U-boot does some things that prevents kernel from working or 
the kernel with the boot stream added on does the right things ?

Thanks,
Bill