[PATCH v3] mtd/nand : workaround for Freescale FCM to support large-page Nand chip
matthieu.castet at parrot.com
Tue Aug 23 06:02:44 EDT 2011
LiuShuo a écrit :
> 于 2011年08月19日 00:25, Scott Wood 写道:
>> On 08/17/2011 09:33 PM, b35362 at freescale.com wrote:
>>> From: Liu Shuo<b35362 at 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 ?
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