[U-Boot-Users] "stacked" memory mapped flash assisted with GPIOs

[Mike Frysinger]

On Monday 21 January 2008, Haavard Skinnemoen wrote:
> Mike Frysinger <vapier at gentoo.org> wrote:
> > - have memory display / flash write commands toggle the GPIO lines
> >  * pros: user interface is transparent and not confusing by making it
> > seem like 1 flash exists (think software raid 0).  able to use 1 write
> > command and the lower layers will automatically split it across multiple
> > flashes.  should work with multiple types of flashes.
> >  * cons: requires modification to cmd_mem.c and cfi_flash.c.
>
> Wouldn't it be enough to just modify the blackfin-specific implementation
> of map_physmem() and unmap_physmem()? Just use some of the physical
> address bits to toggle the necessary GPIO lines and return a suitable
> pointer into the 4MB memory window.

i'm working with u-boot-1.1.6 at the moment (will probably be syncing to 
mainline in the next month or two) so i didnt see these hooks added to the 
cfi_flash.c driver.

that would allow board porters to select an arbitrary address and say "if you 
wish to erase/write the flash in a contiguous manner, you need to use the 
base address 0x........ rather than the real base address 0x........".  
however, from what i can see, this would only account for erase/writes.  
reads are done directly by u-boot using physical addresses, so those have no 
provision for catching accesses.
-mike
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