[U-Boot] freescale i.MX28 mxsboot NAND booting on mx28evk bad blocks

[Paul B. Henson <henson@acm.org>]

On 4/4/2013 3:09 AM, Trent Piepho wrote:

> It's something to do with the way u-boot writes to nand.  If I write
> with nandwrite it doesn't happen, nandtest doesn't find any bad

Hmm, I'm pretty sure I tested burning the u-boot generated nand image 
with nandwrite under Linux with exactly the same result, it seems to be 
inherent in the underlying data, not the burn method.

Did you use the --oob option to nandwrite? The u-boot generated image is 
actually written in two separate steps, the initial piece is written raw 
and includes oob data, the second piece is written normally and the 
ecc/oob is generated by the hardware. To burn it under linux, you need 
to split the u-boot nand image into those two pieces, and write the 
first with -oob, and the second normally.

> A bad block on that chip is marked with a non-0xff as the first OOB
> byte in the 1st page of a block.  So, my guess is that when u-boot
> writes the FCB data it also writes something to the OOB data.

Yes, as would linux if you used the --oob option to nandwrite.

> You said you've booted from NAND.  Did you have to program any of the
> OTP fuses to do this?

No. All I did was install the actual NAND chip and update the boot dip 
switches. Testing u-boot, I followed the script in the default 
environment other than updating it to load the firmware from SD rather 
than tftp. For testing under Linux, I used dd to split the u-boot nand 
image into two pieces, corresponding to the u-boot burn instructions.

> nandwrite didn't seem to want to program the blocks after they were
> marked bad.  The only way fix this seemed to be to scrub nand from
> u-boot.  So it's a problem if you want to be able to flash the
> bootloader from Linux, unless there is some way to get the blocks
> written when they have been marked bad.

No, from what I understand there is no way to clear bad block markers 
from within linux short of modifying the mtd driver.

I followed up with Otavio off list, he said he had ordered some nand 
chips for his board and would get back to me once he had received them 
and had a chance to replicate the issue.

Are you targeting burning the nand with u-boot or linux? If you are 
using an older kernel, the kobs-ng that comes with the mx28 BSP works 
fine. It does not work with newer kernels though, there is a newer 
version of kobs-ng that comes with a different chip BSP that I've heard 
will work correctly on current kernels, it is on my to do list to try it 
out.