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

From: LiuShuo <[email-masked]>
Date: Thu, 1 Sep 2011 17:41:52 +0800

于 2011年08月25日 19:25, Matthieu CASTET 写道:
> 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
>
Sorry for late reply.

After doing some tests, I found that the elbc controller can read/write 
4k with one command
if we insert a FIR_OP_NOP between first half reading/wring and second 
half reading/writing.(delay for something ?)

Read sequence :
-----------------------------------------------------------------------------------------------------------------------
first half :
                out_be32(&lbc->fir,
                          (FIR_OP_CM0 << FIR_OP0_SHIFT) |
                          (FIR_OP_CA << FIR_OP1_SHIFT) |
                          (FIR_OP_PA << FIR_OP2_SHIFT) |
                          (FIR_OP_CM1 << FIR_OP3_SHIFT) |
                          (FIR_OP_RBW << FIR_OP4_SHIFT));

                 out_be32(&lbc->fcr, (NAND_CMD_READ0 << FCR_CMD0_SHIFT) |
                                     (NAND_CMD_READSTART << 
FCR_CMD1_SHIFT));

second half :
                 out_be32(&lbc->fir,
                                 (FIR_OP_RB << FIR_OP1_SHIFT));        
// FIR_OP0_SHIFT is FIR_OP_NOP
-----------------------------------------------------------------------------------------------------------------------

Write sequence :
-----------------------------------------------------------------------------------------------------------------------

first half:
                 fcr = (NAND_CMD_STATUS << FCR_CMD1_SHIFT) |
                       (NAND_CMD_SEQIN << FCR_CMD2_SHIFT) |
                       (NAND_CMD_PAGEPROG << FCR_CMD3_SHIFT);

                 out_be32(&lbc->fir,
                                  (FIR_OP_CM2 << FIR_OP0_SHIFT) |
                                  (FIR_OP_CA << FIR_OP1_SHIFT) |
                                  (FIR_OP_PA << FIR_OP2_SHIFT) |
                                  (FIR_OP_WB << FIR_OP3_SHIFT));

second half:
                 out_be32(&lbc->fir,
                         (FIR_OP_WB << FIR_OP1_SHIFT) |
                         (FIR_OP_CM3 << FIR_OP2_SHIFT) |
                         (FIR_OP_CW1 << FIR_OP3_SHIFT) |
                         (FIR_OP_RS << FIR_OP4_SHIFT));
-----------------------------------------------------------------------------------------------------------------------

I am going to try to finish it and send a new patch.

-LiuShuo