Re: CFI MTD on 5282

Hi Allon,

Allon Stern wrote:
> I've got a custom M5282. We have a memory-mapped MTD.
> 
> Several fun problems here...
> 
> #1: How do I add this device to the baseline 5282 config? It'd be handy 
> to use CFI, as it is a CFI compliant part
> This is my big problem at the moment. I can find examples that seem to 
> deal with SPI, and the guidance I'm getting from a co-worker who added 
> this part to an ARM platform is being of minimal help.....I can find 
> references which are pretty aged. I'm trying to do this on a 2.6 kernel 
> (using the latest baseline. Thanks, Greg!)
> 
> 
> #2: this device is a 64MB part. Fun, since we don't have quite the 
> number of address lines we need. The hardware designer ran CS2 and CS3 to
> the high order address lines. (A24/A25)
> 
> I've decided to configure CS2 and CS3 as GPIOs and drive it as a banked 
> MTD. Is this possible?
> The chip appears as two stacked chips with a common chip select, and the 
> A25 selects the die.
> I can bank them on the high order address line; I MIGHT be able to get a 
> revision which ANDs the CS0 going to the chip with CS2 going to A24 on 
> the flash, which would let me set up two chip selects to get a 
> contiguous memory space for it;
> Anyone know if CFI will get all munged up if the top and bottom halves 
> of the memory are reversed? That is, if the base address points to the 
> top half of the chip, and the middle address points to the bottom?
> 
> And without that revision, is it possible to do a banked MTD with the 
> bank selecting two halves of a single strataflash part? (I'd have four 
> banks, each one half of a die, and two dies)
> 
> (it's a Numonyx P30 strataflash, FWIW)

You can do pretty much any weird translation you like in your own
MTD map driver. You just need to write access functions (the
read/write/... functions in struct map_info) that do appropriate
GPIO twidling and address translation on the supplied linear address,
and return appropriate data. Once they work you can do a cfi_probe
and it should work. (The bank switching is hidden in the accessor
functions).

Or am I mis-understanding what you want to do?

Regards
Greg


------------------------------------------------------------------------
Greg Ungerer  --  Chief Software Dude       EMAIL:     [email protected]
Secure Computing Corporation                PHONE:       +61 7 3435 2888
825 Stanley St,                             FAX:         +61 7 3891 3630
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