Re: [PATCH 5/7] add GPMI support for imx28

[Florian Fainelli <ffainelli@freebox.fr>]

Hello,

On Wednesday 23 March 2011 15:56:24 Lothar Waßmann wrote:
> Hi,
> 
> Huang Shijie writes:
> > Hi Lothar:
> >     Thanks a lot for your carefully review.
> > > 
> > > Hi,
> > > 
> > > 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.
> 
> > [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?

I suppose this is the way it should be done, but then you might some need some 
sort of NAND detection available before registering the driver. Eventually, 
the bootloader might have configured the appropriate timings already.

Have you considered using ONFI chips? They have standard timings at least.

> 
> > > - What is the purpose of the 'rom_helpers'? To me it looks like they
> > > 
> > >    are doing something that should be done in the mtd partition
> > >    handlers, not in the flash chip driver.
> > 
> > We have saled a lot products based the imx23 or imx28.
> > All the products support the nand boot mode by flashing the kernel to
> > the kernel partitions of the nands.
> > In order to compliant to the old product, the layout of the nand is
> > constraint to the current situation:
> > [1] first a boot partition for the kernel.
> > [2] the rest is for other uses, such as rootfs.
> > 
> > So I have to use the rom_helpers to split the kernel partition before
> > the real MTD partition initializations.
> 
> Why can't you just create appropriate partitions using the standard
> partition handlers?
> 
> 
> Lothar Waßmann