Subject: Re: [PATCH v3] mtd/nand : workaround for Freescale FCM to support large-page Nand chip

From: Matthieu CASTET <[email-masked]>
Date: Thu, 25 Aug 2011 13:25:39 +0200

Hi,

LiuShuo a écrit :
> 于 2011年08月23日 18:02, Matthieu CASTET 写道:
>> LiuShuo a écrit :
>>> 于 2011年08月19日 00:25, Scott Wood 写道:
>>>> On 08/17/2011 09:33 PM, [email-masked] wrote:
>>>>> From: Liu Shuo<[email-masked]>
>>>>>
>>>>> Freescale FCM controller has a 2K size limitation of buffer RAM. In order
>>>>> to support the Nand flash chip whose page size is larger than 2K bytes,
>>>>> we divide a page into multi-2K pages for MTD layer driver. In that case,
>>>>> we force to set the page size to 2K bytes. We convert the page address of
>>>>> MTD layer driver to a real page address in flash chips and a column index
>>>>> in fsl_elbc driver. We can issue any column address by UA instruction of
>>>>> elbc controller.
>>>>>
>>>>> NOTE: Due to there is a limitation of 'Number of Partial Program Cycles in
>>>>> the Same Page (NOP)', the flash chip which is supported by this workaround
>>>>> have to meet below conditions.
>>>>> 	1. page size is not greater than 4KB
>>>>> 	2.	1) if main area and spare area have independent NOPs:
>>>>> 			  main  area NOP    :>=3
>>>>> 			  spare area NOP    :>=2?
>>>> How often are the NOPs split like this?
>>>>
>>>>> 		2) if main area and spare area have a common NOP:
>>>>> 			  NOP               :>=4
>>>> This depends on how the flash is used.  If you treat it as a NOP1 flash
>>>> (e.g. run ubifs rather than jffs2), then you need NOP2 for a 4K chip and
>>>> NOP4 for an 8K chip.  OTOH, if you would be making full use of NOP4 on a
>>>> real 2K chip, you'll need NOP8 for a 4K chip.
>>>>
>>>> The NOP restrictions should be documented in the code itself, not just
>>>> in the git changelog.  Maybe print it to the console when this hack is
>>>> used, along with the NOP value read from the ID.
>>> We can't read the NOP from the ID on any chip. Some chips don't
>>> give this infomation.(e.g. Micron MT29F4G08BAC)
>> Doesn't the micron chip provide it with onfi info ?
> Sorry, there is something wrong with my expression.
> We can get the NOP info from datasheet, but can't get it by READID 
> command in code.
> 
ok I was thinking the micron chip was a 4K nand. But it is an old 2K. Why do you
want NOP from it ?

Also can you reply my question about the sequence you use when trying to read 4k
with one command.

Thanks

Matthieu