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

[Matthieu CASTET <matthieu.castet@parrot.com>]

LiuShuo a écrit :
> 于 2011年08月19日 00:25, Scott Wood 写道:
>> On 08/17/2011 09:33 PM, b35362@freescale.com wrote:
>>> From: Liu Shuo<b35362@freescale.com>
>>>
>>> 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 ?

Matthieu