[PATCH 5/7] add GPMI support for imx28

[Huang Shijie]

Hi Lothar:

> Hi,
>
> Huang Shijie writes:
>> Hi Lothar:
>>>>> some general comments:
>>>>> - Why are you not using the existing nand_ids but inventing your own
>>>>>      database?
>>>>>
>>>> The nand_ids{} contains poor information for me.
>>>> Such as :
>>>> [1]The nand_ids does not have the enough information for the page
>>>> size,oob size for some new NANDs.
>>>>       And you can not get the information from parsing the NAND ids, such
>>>> as some Micron NANDs.
>>>>
>>> You could use it for the standard chips where you do not need
>>> additional information. That way most NAND chips could be supported
>>> out of the box without having to modify the driver.
>>>
>> What the meaning of "standard chips"?
>>
> Those chips that are supported by other drivers for long time.
>
see belowing.
>> There are many nands in the world. Every vendor has its own rules, some
>> even does has :)
>>
>> Unluckily, the imx23/imx28 supports many nands that the nand_ids{} does
>> not support.
>>
> That's no reason to scrap support for all chips that every other
> driver supports.
>
Frankly speaking, Which nand we should to support depends on the 
customer's requires.

So we really do not want to support other nands that the customer does 
not have.

>> I have many nands by my hand. I will add it gradually.
>>
> So why not add them to the generic database?
>
I ever thought to change the generic database. But I found it would cost 
a long time.

The parsing code in nand_get_flash_type() can not parse out the page 
size/oob size
in some cases. And IMHO I do not think to get the page size/oob size by 
parsing the ids is a good way,
this really makes the code mess (sorry, David, I really think the 
current code is ugly.).

IMHO, the best solution is add a database like mine. Using the id bytes 
as the keyword to match the nand.
then to get the page size /oob size , etc, from the database.

I will send a patch about this in future, but now, I do not want to  be 
stumbled by this problem.




>> I want to get the page size/oob size from my own database which can not
>> get from the nand_ids.
>>
> If there are parameters needed that cannot be obtained from the
> generic database, it might be worth upgrading that database instead of
> creating your own local database.
>
>>>> [2]I need the timing information of the NAND. The nand_ids DOES not have
>>>> it. I have to
>>>>       read the datasheet of the NAND, and add it to my database.
>>>>
>>> Do we really need exact timing data for each individual chip?
>>> Or couldn't we live with some sane timing that works for most chips
>>> and provide some means to specify a different timing via
>>> platform_data?
>>>
>> Most of the time, the timing is really based on a safe timing setting.
>> But in the original GPMI driver in the FREESCALE BSP, there exits some
>> nands need to be set with their own timing setting.
>>
>> So I do not use the safe timing for _ALL_ the nand, and i'd better get
>> it from the
>> database.
>>
> It should be sufficient to provide timing info from platform_data in
> special cases instead of bloating the nand id database with that
> stuff. Platforms might need to adjust the timing because of
> peculiarities in the HW. Thus the timing info should be provided from
> there, not from the chip database.

The timing information is needed by the GPMI module, not other module. 
So the
best way to get this is from the chip database.

Setting the GPMI with the proper timing will make the NAND runs in high 
performance.

Thanks for your advice, I will use the safe timing for all the nand.

Huang Shijie