Re: NAND detect

[Ben Dooks <ben-mtd@fluff.org>]

On Wed, Sep 22, 2004 at 05:55:20PM +0200, lp4u@inwind.it wrote:
> Hi,
> 
> I have a s3c2410 board (BAST architecture).
> I have installed on board a kernel2.4.26 patched and with MTD.
> But the board, at boot, don't detect the NAND (I've 3 NANDs on board: 2 samsung & 1 STM).

Does the bootloader list them, newish versions of the bootloader
should probe all available devices and print the ID information
it finds as it goes.

> The MTD detect only NOR Flash.

I've just had a check through, and it seems the driver was
written pre the nand hooks for >1 chip per controller, and
therefore just selects slot 0 (smartmedia card) at start time.

A quick way to get going would be to change the value passed
to bast_nand_select_slot() in bast_nand_init() in the driver
to at least show that a chip can be detected and used. The
current default in the driver is to select the SmartMedia socket.

The slots are allocated as 0 for the SmartMedia card slot, and
1 through 3 for the chips on the board (U52, U53 and U54)

Looking through the NAND code, it seems that we may have a
few problems with implementing >1 chip, which could bite
in your configuration:

1) The driver needs to work out which slots are used and
   create a linear mapping of chips -> slots.

2) The NAND layer itself seems to concatenate the chips
   together, not export them as seperate devices, which
   makes supporting removable devices in the card slot
   and on-board NAND difficult.

I would be interesting in anyone's comments about how difficult
it would be to have an overall controller activity lock and
allow a single controller to register more than one NAND chip
as a seperate device. 

It would also be nice to have at least some form of hotplug
mechanism support where a chip can be re-scanned after a
change in it's detect status.

-- 
Ben (ben@fluff.org, http://www.fluff.org/)

  'a smiley only costs 4 bytes'