[ECOS] NAND support

[Rutger Hofman]

Simon Kallweit wrote:
> Hi there
> 
> I was wondering what the current state of the NAND subsystem from Rutger 
> Hofman is. I'm currently working on a port of the UFFS filesystem 
> (http://gouffs.googlepages.com/) which is intended to work on NAND 
> flash. Are there any major arguments against merging his code into the 
> eCos trunk? Anything that needs to be addressed? I would be willing to 
> contribute a synth NAND driver as well as support for the STM32 target.

There have been 2 test platforms:
1) I have a BlackFin EZ-Kit BF548
      - this type of BlackFin has an on-board NFC (NAND Flash 
Controller), with support for ECC
      - it has one NAND flash chip of the regular class
2) Televic's custom board
      - Atmel AT91SAM9260 with an on-board NFC. Although it has hardware 
ECC support of the "syndrome", Televic used software ECC
      - it has one NAND flash chip of the regular class
      - Televic didn't publish their NFC driver

Both platforms use YAFFS with the interface layer that I wrote.

Televic didn't report any errors (except one place w/ a wrongly assigned 
value -- which wasn't used).

Both Televic and I exercised the YAFFS file-system tests that I copied 
to YAFFS from other file system implementations.

The status therefore is:

+ runs for BlackFin NFC
+ runs for AT91SAM9260 NFC
+ runs for one regular NAND chip
+ runs for YAFFS
+ no open issues

- no tests for multiple or heterogeneous chips
- no tests for multiple or heterogeneous chips
- no tests for "syndrome" ECC
- no tests for small-page chips -- they have a different command set
- no tests for ONFI chips -- I still have to see one!

In conclusion, the status is that I would love to see more and varied 
tests before the package could be declared stable. Also, feedback on the 
design is still very welcome. Televic reported that implementing an NFC 
driver for their AT91SAM9260 was rather troublesome, although I don't 
know what kind of problems they had to solve. I tried to improve my 
documentation when I heard that :-).

I intend to merge this package into mainline eCos. I don't know what a 
good time is: now, or when it has been stressed a bit more.

Rutger

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