[U-Boot] omap4460 nand booting ?

[Abraham Varricatt]

Hello,

Thanks to the help I obtained on this mailing list, I've been able to
customize u-boot (2013.10 release) to work on a custom omap4460 board.
Schematically, it's similar to the pandaboard, but uses the twl6032
pmic and has a NAND memory from micron present.

I've been able to boot this board from USB and from an external mmc
card. In both cases, I've been able to access the nand memory (i.e.
reading/writing). My team tried writing an image of the linux kernel
to the nand from mmc, rebooted the board, copied the image from nand
to ddr and booted off it. At the very least, we feel that this shows
that the memory is working properly.

The problem I'm facing is that I can't seem to boot directly from the
nand memory chip. We've set the boot configuration pins to start with
NAND boot, but it doesn't seem to work. On probing the CS and
nand-busy lines we can see some activity happening, but don't
understand what it means.

The way I expect the board to work, is that the ROM code should detect
the external nand present, query for ONFI data, configure the
bus/interface accordingly, copy SPL part of bootloader from first
sector to internal sram and boot off that.

I *think* that the omap4460 is sending the ONFI request, but after
that, something malfunctions, nand is deemed unusable and the next
device in boot sequence is queried. In my case its the uart and I can
see some garbage characters coming out on the console.

Any suggestions on how I could debug this?

-Abraham V.