a complex map

[Mike Frysinger]

On Mon, Sep 8, 2008 at 2:44 PM, Allon Stern wrote:
> I've got the unique pleasure of dealing with a hardware design
> cramming a 64MB NOR flash onto a 23 bit address bus (Coldfire M5282).
> The memory chip is a Numonyx Strataflash (P30). It's a single part on
> a 16 bit data bus.
>
> A couple of questions:
> #1: this chip appears as two dies; Each die has four small (32K)
> blocks at the bottom, with 128K blocks elsewhere. Is this a problem,
> particularly if the small blocks appear in the middle of an MTD
> partition? I'm assuming no problem. (I have concatenating support
> enabled to allow my partition to span the two dies)

the mtd layers handle bottom/top boot devices just fine. usually
people use those sectors to store configurations or bootloaders rather
than filesystems though.  but that is of course your choice.

> #2: I control the high two address bits on the flash (A24 and A25)
> using GPIOs. I have a customized map for this flash which sets the
> GPIOs appropraitely for the offset being accessed. Is this is all I
> need to do?

ive written a generic gpio mapping driver but i'm not sure it's been
posted to LKML yet ... perhaps you will find it useful:
http://blackfin.uclinux.org/git/?p=readonly-mirrors/linux-kernel.git;a=blob_plain;f=drivers/mtd/maps/gpio-addr-flash.c;hb=HEAD

example platform resources can be found here:
http://blackfin.uclinux.org/git/?p=readonly-mirrors/linux-kernel.git;a=commitdiff;h=cf8a23b05d657efbe704426ac458db2f219f5bef

and here:
http://blackfin.uclinux.org/git/?p=readonly-mirrors/linux-kernel.git;a=blob_plain;f=arch/blackfin/mach-bf537/boards/tcm_bf537.c;hb=HEAD
-mike