how to get MTD support - need expert input

how to get MTD support - need expert input

[Tim Hockin]

Hello, All.

I am trying to get the general MTD layer in linux to support our systems'
flashroms.  The problem is that our system setup is a bit unique.

We have 1 or 2 chips (so far all have been JEDEC).  These may be of
intermixable sizes from 512K to 4MB.  They are mapped in the top 64k of
address space (x86 compatible).  To swap pages and banks, there is a custom
flash page register, which has a few bits that determine teh actively
mapped page.

So my question is this:

What is the best way for me get full support?  Apparently all the JEDEC
support in 2.4.5 is broken.

This is my thought:

have a map driver (like the other chipset map drivers) that builds it's own
struct mtd_info.  We can then flip pages at will, probe however we like,
etc.  I wish I could say that we will always have both flash chips
identical, but I can't.

feedback?

-- 
Tim Hockin
Systems Software Engineer
Sun Microsystems, Cobalt Server Appliances
thockin@sun.com

Re: how to get MTD support - need expert input

[David Woodhouse]

thockin@sun.com said:
>  What is the best way for me get full support?  Apparently all the
> JEDEC support in 2.4.5 is broken.

Don't even look at the MTD support in 2.4.5. Use 2.4.6-pre3 or later.
There should be something in that which should drive the chip - out of the 
jedec.c code, the amd_flash.c code and the hack which detects such flash 
chips and uses the CFI driver backend.

If the chips are different you'll need to register them in separate 'map' 
drivers - we don't currently support having different chips in the same 
mapping, although that's relatively easily fixable if it's absolutely 
necessary.

Take a look a drivers/mtd/octagon-5066.c for inspiration. Get your mapping 
driver working with the map_rom chip driver first and then we can worry 
about the flash in it.

What flash chips are you likely to be using?

--
dwmw2

Re: how to get MTD support - need expert input

[Ian]

I was looking at having one of these made for me ... if its XIP flash (unlike
the DoC Millennium (outside its first 512bytes)) then I would be interested
in the circuit diagrams and could contribute C-level programming to drive it
resources.

Actually the one I was looking at having built would have been 512k pages,
but 64k should be enough for anybody ;-)



  ----- Original Message -----
>From: "Tim Hockin" <thockin@sun.com>
>To: <linux-mtd@lists.infradead.org>
>Subject:  how to get MTD support - need expert input
>Date: Tue, 12 Jun 2001 20:35:27 -0700
>
> Hello, All.
> 
> I am trying to get the general MTD layer in linux to support our systems'
> flashroms.  The problem is that our system setup is a bit unique.
> 
> We have 1 or 2 chips (so far all have been JEDEC).  These may be of
> intermixable sizes from 512K to 4MB.  They are mapped in the top 64k of
> address space (x86 compatible).  To swap pages and banks, there is a 
custom
> flash page register, which has a few bits that determine teh actively
> mapped page.
> 
> So my question is this:
> 
> What is the best way for me get full support?  Apparently all the JEDEC
> support in 2.4.5 is broken.
> 
> This is my thought:
> 
> have a map driver (like the other chipset map drivers) that builds it's own
> struct mtd_info.  We can then flip pages at will, probe however we like,
> etc.  I wish I could say that we will always have both flash chips
> identical, but I can't.
> 
> feedback?
> 
> -- 
> Tim Hockin
> Systems Software Engineer
> Sun Microsystems, Cobalt Server Appliances
> thockin@sun.com
> 
> ______________________________________________________
> Linux MTD discussion mailing list
> http://lists.infradead.org/mailman/listinfo/linux-mtd/
> 

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