From: Peter Barada <peter.barada@logicpd.com>
To: u-boot@lists.denx.de
Subject: [U-Boot] NAND flash question
Date: Mon, 23 Sep 2013 13:02:12 -0400 [thread overview]
Message-ID: <52407414.7050805@logicpd.com> (raw)
In-Reply-To: <F9C551623D2CBB4C9488801D14F864C639AD1190@ex-mb1.corp.adtran.com>
On 09/20/2013 11:27 AM, ANDY KENNEDY wrote:
>> -----Original Message-----
>> From: u-boot-bounces at lists.denx.de [mailto:u-boot-bounces at lists.denx.de] On Behalf Of Peter Barada
>> Sent: Thursday, September 19, 2013 3:26 PM
>> To: u-boot at lists.denx.de; Peter Barada
>> Subject: Re: [U-Boot] NAND flash question
>>
>> On 09/19/2013 04:04 PM, ANDY KENNEDY wrote:
>>> All,
>>>
>>> We have a design that has NAND as a secondary device (not the boot
>>> device). The last four pages of the NAND flash are reported as bad.
>>> Should this be true for all NAND flash devices we have?
>>>
>>>
>> No, I wouldn't think so. Manufacturers qualify their parts and mark bad
>> blocks found during qualification testing. Most data sheets indicate
>> that the number of bad blocks marked bad during manufacturer is below a
>> set percentage(if above thent he part is rejected). Some parts that are
>> meant to be used during boot (such as NAND meant for OMAP parts) will
>> have certain blocks that are guaranteed good (i.e. the boot blocks).
>> Past that bad blocks could be anywhere in a particular device.
>>
> Okay, well, next question: So on EVERY unit we have designed with a
> NAND flash, when u-Boot reads the NAND flash it reports that it couldn't
> locate a bad block table and states that it cannot read the last four
> pages of the flash. Next, when one does a 'nand bad' on these boards,
> these last four pages are reported by u-Boot as bad. Looking at the
> code, we believe that this is by design. Is that correct? Has anyone
> else done a 'nand bad' on a board and seen the same information?
>
> Thanks again for any information you can provide,
>
> Andy
If you are using a NAND-based bad block table (i.e. set the
NAND_USE_FLASH_BBT bit in nand->options), then the MTD layer will
internally use the last four blocks to hold the bad block table _and_
report those blocks as bad to prevent the user from accidentally
modifying them...
--
Peter Barada
peter.barada at logicpd.com
prev parent reply other threads:[~2013-09-23 17:02 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-19 20:04 [U-Boot] NAND flash question ANDY KENNEDY
2013-09-19 20:25 ` Peter Barada
2013-09-20 15:27 ` ANDY KENNEDY
2013-09-23 17:02 ` Peter Barada [this message]
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