John Tobias wrote:
Hi,
Sorry for the messed up. I was forwarding your email to my co-worker
and I accidentally send it to you.
Anyway, I have a few questions to follow up with you guys.
1. What are the possible cause of the "read disturb errors"?. Can you
give me a bit detail explanation?
You will find information on read disturb in the datasheet for your NAND
part. Here is an excerpt from a Micron appnote.
*From Micron App note:
**_http://download.micron.com/pdf/technotes/nand/tn2917.pdf_*
*Read Disturb:* A read disturb error occurs when one or more bits are
changed from “1”
to “0” during a READ operation. Read disturb errors occur within the
block being read,
but on a page or pages other than the page being read. Performing a high
number
(hundreds of thousands or millions) of READ operations on individual
pages before an
ERASE command for the block containing those pages can exacerbate this
error.
To recover from this type of error, erase the block where the error
occurred and reprogram
the data to that block.
------------------------------------------------------------------------------------
Accessing this code repeatedly, without erasing and
reprogramming the data, causes errors to occur over time (see “Temporary
Failures” on
page 2). Many factors influence the point at which errors begin to
appear, including how
often the same physical area of the NAND Flash device is read and the
extent to which
ECC is used to maintain data integrity in the system.
Also see:
_http://www.edn.com/blog/980000298/post/1670047767.html_
2. I am using kernel 2.6.10 and the ECC that we are using is
NAND_ECC_HW3_512. Brian, in your suggestions (reading the failing
blocks), how I can possible access the nand blocks if am getting a
constant "BOOTME BOOTME ..." on my serial port?. Do you have any tools
that I can use?
You can modify DVFlasher to read blocks from NAND and output over
serial. You are basically adding a command to ubl. Look at
DVFlasher.cs and uartboot.c. It is likely more busywork than not, but
it's nice to verify. There may be better tools than DVFlasher as well
out there, but I am not familiar with any of them.
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