Re: JFFS2 NAND flash support

[Thomas Gleixner <gleixner@autronix.de>]

On Wednesday, 27. March 2002 18:42, John Hall wrote:
> I'm wanting to get JFFS2 to go on some NAND flash (it's actually
> Smartmedia, but it's pretty much just NAND flash) with a 2.4.17 kernel.
It is exactly NAND flash, molded in thin plastic

> I've adapted the NAND flash driver in the kernel tree and that now seems
> to work for me.
maybe you have done duplicated work . See below.

> The jffs2 stuff in my kernel sources doesn't seem very up to date so
> I've got the latest CVS stuff. Which branch of cvs do I need to use?
> Should I update the whole of the mtd subsystem or can I just use the
> updated jffs2 stuff?
The current developer branch. Take care there were a lot of changes in nand.c 
and hardware driver files. See nand.c / autcpu12.c
Adaptions should made in hardware drivers like autcpu12 and not in nand.c
If there's a neccecarity to do this, please contact me or David Woodhouse.

> I also came across some problems with the existing NAND flash driver,
> especially with erases. It doesn't seem to mark an erase as done,
>   i.e. instr->state = MTD_ERASE_DONE;
It's fixed in CVS long ago

> Also, when doing an erase it obtains a spin lock that disables all
> bottom halves from running. It holds this lock for the duration of the
> erase, which is up to 4ms in the code - is this really a good idea? The
> Smartmedia specs say that this delay can be up to 400ms! Definitely not
> a good idea.
There's no better to ensure, that erase read and write can coexist at the 
moment. But you're invited to hack a better solution :)

I this a new card type ? All chips and card types I know, have maximum block 
erase times of 20ms.

-- 
Thomas
_________________________________
Thomas Gleixner <gleixner@autronix.de>
autronix automation http://www.autronix.de