[PATCH] powerpc: Create "rom" (MTD) device prpmc2800

[David Woodhouse]

On Mon, 2007-06-04 at 00:26 +0400, Sergei Shtylyov wrote:
>     Erm, FSL boards seem to generally have dual 16-bit NOR flash chips 
> interleaved -- and that's seems quite a common case, not only in PPC world.

Yes, it's something we've seen quite frequently. It's a common way of
improving read/write/erase speed.

>     Perhaps... those interleaved chips could really be merged (abstracted) 
> into a single one, with the bus width being a sum of two?

That's how Linux deals with it, as I'm sure you're aware. Other
operating systems do likewise. If two 'separate' flash chips hold
alternate bytes of a given address range, you really don't gain much by
representing them as two separate devices to the system.

Any representation of flash devices in the device-tree should ideally
have 'bus width' and 'interleave' properties to contain this
information.

The 'bus width' cannot necessarily be inferred, especially where a given
bus can be configured to allow multiple sizes of access. It's purely a
function of how the flash chips are wired up. That's why we actually
call it 'bank width', not 'bus width' in the Linux code.

-- 
dwmw2