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

Hi,

LiuShuo a écrit :

于 2011年08月23日 18:02, Matthieu CASTET 写道:

quoted

LiuShuo a écrit :

quoted

于 2011年08月19日 00:25, Scott Wood 写道:

quoted

On 08/17/2011 09:33 PM, b35362@freescale.com wrote:

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From: Liu Shuo<redacted>

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?

quoted

		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