[U-Boot] NAND flash - bad blocks
Hello,
First of all sorry if this question was already answered here.
We are sourcing some K9F8G08U0M-PIB0 NAND flash devices. On the first erase in uboot 2011.09 I got bunch of mostly consecutive bad blocks. According to the datasheet we should get not more then 80 bad blocks for our chip but I get something like 240 bad blocks for most of the NAND chips.
I seems to be able to fix this using the following procedure:
In uboot uboot>nand scrub.chip
In uboot uboot>nand erase.chip clean at this point I get usually 1,2 bad blocks which looks normal to me.
In Linux we have few mtd partitions on this NAND chip. Unmount all of them and for all of them : linux>nandtest -m /dev/mtdx Usually this doesn't add any new badblocks on top of what I get on nand erase in uboot, but I really haven't tested that much device to say.
After this procedure the NAND flash seems to work fine. Do you think this is reliable way? Is there something better I can do?
Has anyone got NAND component batch having more bad blocks then datasheet allows. Should we consider the provider unreliable?
Thank you Dimitar
On 01/10/2013 01:56:30 AM, Dimitar Penev wrote:
Hello,
First of all sorry if this question was already answered here.
We are sourcing some K9F8G08U0M-PIB0 NAND flash devices. On the first erase in uboot 2011.09 I got bunch of mostly consecutive bad blocks. According to the datasheet we should get not more then 80 bad blocks for our chip but I get something like 240 bad blocks for most of the NAND chips.
I seems to be able to fix this using the following procedure:
Call your NAND vendor and complain?
After making sure that there's nothing wrong with your NAND driver or controller that causes the OOB to be read incorrectly. Did you do anything to the NAND chip prior to this "first erase"? In particular, did you write to the OOB?
In uboot uboot>nand scrub.chip
In uboot uboot>nand erase.chip clean at this point I get usually 1,2 bad blocks which looks normal to me.
You're not fixing anything -- you're wiping out all bad block information. Those "1,2 bad blocks" are not actually bad blocks, but are the bad block table which appears "bad" to reserve it. These should be at the end of flash. Or, possibly, they're blocks that happen to be damaged in a way that prevents the bad block marker from becoming 0xff.
In Linux we have few mtd partitions on this NAND chip. Unmount all of them and for all of them : linux>nandtest -m /dev/mtdx Usually this doesn't add any new badblocks on top of what I get on nand erase in uboot, but I really haven't tested that much device to say.
After this procedure the NAND flash seems to work fine. Do you think this is reliable way?
No.
-Scott
Hi Scott,
On 01/10/2013 01:56:30 AM, Dimitar Penev wrote:
Hello,
First of all sorry if this question was already answered here.
We are sourcing some K9F8G08U0M-PIB0 NAND flash devices. On the first erase in uboot 2011.09 I got bunch of mostly consecutive bad blocks. According to the datasheet we should get not more then 80 bad blocks for our chip but I get something like 240 bad blocks for most of the NAND chips.
I seems to be able to fix this using the following procedure:
Call your NAND vendor and complain?
Well we did but we didn't got something from them which could explain what we observe.
After making sure that there's nothing wrong with your NAND driver or controller that causes the OOB to be read incorrectly.
We are using nand_plat driver provide by ADI without any customization.
Did you do anything to the NAND chip prior to this "first erase"? In particular, did you write to the OOB?
For boards coming out of the assembly house: I load uboot in SPI flash, boot from SPI and get the NAND chip recognized properly. On 'nand erase.chip' command I get bunch of bad blocks. So I guess we haven't even touched OOB before 'nand erase'
Assuming the components are OK the only possible explanation could be overheating of the chips in the assembly house. Does anybody get something similar?
In uboot uboot>nand scrub.chip
In uboot uboot>nand erase.chip clean at this point I get usually 1,2 bad blocks which looks normal to me.
You're not fixing anything -- you're wiping out all bad block information. Those "1,2 bad blocks" are not actually bad blocks, but are the bad block table which appears "bad" to reserve it. These should be at the end of flash. Or, possibly, they're blocks that happen to be damaged in a way that prevents the bad block marker from becoming 0xff.
Oh Really? What about 'nandtest -m' in Linux ? I was hoping it does a check of the erase blocks.
In Linux we have few mtd partitions on this NAND chip. Unmount all of them and for all of them : linux>nandtest -m /dev/mtdx Usually this doesn't add any new badblocks on top of what I get on nand erase in uboot, but I really haven't tested that much device to say.
After this procedure the NAND flash seems to work fine. Do you think this is reliable way?
No.
Thanks Scott. Is there any procedure to analyze the nand flash for bad blocks?
-Scott
Best Regards Dimitar
On 01/11/2013 02:46:06 AM, Dimitar Penev wrote:
Hi Scott,
On 01/10/2013 01:56:30 AM, Dimitar Penev wrote:
Hello,
First of all sorry if this question was already answered here.
We are sourcing some K9F8G08U0M-PIB0 NAND flash devices. On the first erase in uboot 2011.09 I got bunch of mostly consecutive bad blocks. According to the datasheet we should get not more then 80 bad blocks for our chip but I get something like 240 bad blocks for most of the NAND chips.
I seems to be able to fix this using the following procedure:
Call your NAND vendor and complain?
Well we did but we didn't got something from them which could explain what we observe.
After making sure that there's nothing wrong with your NAND driver or controller that causes the OOB to be read incorrectly.
We are using nand_plat driver provide by ADI without any customization.
Still, do some investigation to see whether it seems to be working. Dump the raw data that you read -- is it mostly 0xff with some bad block markers set, or is it returning garbage? Do any of the blocks that are not marked bad have non-0xff data? If you do a scrub of the entire NAND chip, then write to one block, does the write show up anywhere else on the NAND chip?
In uboot uboot>nand scrub.chip
In uboot uboot>nand erase.chip clean at this point I get usually 1,2 bad blocks which looks normal to me.
You're not fixing anything -- you're wiping out all bad block information. Those "1,2 bad blocks" are not actually bad blocks, but are the bad block table which appears "bad" to reserve it. These should be at the end of flash. Or, possibly, they're blocks that happen to be damaged in a way that prevents the bad block marker from becoming 0xff.
Oh Really? What about 'nandtest -m' in Linux ? I was hoping it does a check of the erase blocks.
That's no substitute for having the factory bad block markers. Nandtest doesn't look very rigorous at all -- and only seems to mark bad blocks if the erase or write operations return failure, not if it sees an uncorrectable error on readback.
Thanks Scott. Is there any procedure to analyze the nand flash for bad blocks?
Yes, and it's done by the flash manufacturer to produce bad block markers. :-P
-Scott
Hi Scott,
I have tried to do some more tests on the board with the NAND chip I have scrub-ed
-I have done 'nand erase.chip clean' and tried to probe different nand regions (I have 128MB RAM and 1GB NAND and I am not sure how I could dump the whole NAND at once) It seems the whole NAND is 0xFF
After that I have written 10MB at the beginning of the NAND and those data was verified to be written OK Outside of the 10MB region the NAND stays 0xFF
in Linux 'nandtest' doesn't report any issue.
So I tend to think that nand scrub did a good think for me.
Best Regards Dimitar
----- Original Message ----- From: "Scott Wood" scottwood@freescale.com To: "Dimitar Penev" dpn@switchfin.org Cc: u-boot@lists.denx.de Sent: Friday, January 11, 2013 10:21 PM Subject: Re: [U-Boot] NAND flash - bad blocks
On 01/11/2013 02:46:06 AM, Dimitar Penev wrote:
Hi Scott,
On 01/10/2013 01:56:30 AM, Dimitar Penev wrote:
Hello,
First of all sorry if this question was already answered here.
We are sourcing some K9F8G08U0M-PIB0 NAND flash devices. On the first erase in uboot 2011.09 I got bunch of mostly consecutive bad blocks. According to the datasheet we should get not more then 80 bad blocks for our chip but I get something like 240 bad blocks for most of the NAND chips.
I seems to be able to fix this using the following procedure:
Call your NAND vendor and complain?
Well we did but we didn't got something from them which could explain what we observe.
After making sure that there's nothing wrong with your NAND driver or controller that causes the OOB to be read incorrectly.
We are using nand_plat driver provide by ADI without any customization.
Still, do some investigation to see whether it seems to be working. Dump the raw data that you read -- is it mostly 0xff with some bad block markers set, or is it returning garbage? Do any of the blocks that are not marked bad have non-0xff data? If you do a scrub of the entire NAND chip, then write to one block, does the write show up anywhere else on the NAND chip?
In uboot uboot>nand scrub.chip
In uboot uboot>nand erase.chip clean at this point I get usually 1,2 bad blocks which looks normal to me.
You're not fixing anything -- you're wiping out all bad block information. Those "1,2 bad blocks" are not actually bad blocks, but are the bad block table which appears "bad" to reserve it. These should be at the end of flash. Or, possibly, they're blocks that happen to be damaged in a way that prevents the bad block marker from becoming 0xff.
Oh Really? What about 'nandtest -m' in Linux ? I was hoping it does a check of the erase blocks.
That's no substitute for having the factory bad block markers. Nandtest doesn't look very rigorous at all -- and only seems to mark bad blocks if the erase or write operations return failure, not if it sees an uncorrectable error on readback.
Thanks Scott. Is there any procedure to analyze the nand flash for bad blocks?
Yes, and it's done by the flash manufacturer to produce bad block markers. :-P
-Scott
On 01/15/2013 05:09:16 AM, Dimitar Penev wrote:
Hi Scott,
I have tried to do some more tests on the board with the NAND chip I have scrub-ed
-I have done 'nand erase.chip clean'
Don't specify "clean". That will cause jffs2 cleanmarkers to be written. Not all NAND chips can handle partial programming, and in any case it's an unnecessary variable for figuring out the bad block situation.
and tried to probe different nand regions (I have 128MB RAM and 1GB NAND and I am not sure how I could dump the whole NAND at once) It seems the whole NAND is 0xFF
Including OOB?
So I tend to think that nand scrub did a good think for me.
No, it didn't. You are ignoring the problem.
-Scott
participants (2)
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Dimitar Penev -
Scott Wood