[U-Boot] Non standard CFI detection tweaks

[Stefan Roese]

Hi Rogan,

On Thursday 12 August 2010 14:07:03 Rogan Dawes wrote:
> I found the following configuration snippet for OpenOCD for the DNS323
> at http://wiki.dns323.info/hardware:jtag:
> 
> #          driver   addr       size     chip_width  bus_width  options
> flash bank cfi      0xff800000 0x800000 1           2          0
> 
> It seems that the key here is that the bus_width is set to 2, even
> though the chip_width is only 1.

Seems not to be so uncommon: 8bit device on a 16bit external bus.
 
> Also, the flash address is still 0xff800000, even though the kernel has
> it as 0xf4000000. I guess this is because only a certain number of
> address lines are actually connected through to the flash chip, and so
> the chip can appear in multiple places?

Yes, this could be the case. The flash is most likely "mirrored".
 
> Does that make any more sense? Is it possible that the CFI code in
> U-Boot doesn't consider the case when bus_width == 2?

As mentioned above, this seems to be a common use-case (even though I don't 
have such a board at hand right now). Bus-width = 2 (vs. bus-width = 1) 
shouldn't really matter here. A CPU byte access to the flash address space 
should translate in one access cycle (8-bit) to the flash device.

Sorry, no real idea whats going wrong without being able to test/debug on this 
platform.

Cheers,
Stefan

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