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.
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