[PATCH 04/14] bus: mvebu-mbus: Add static window allocation to the DT binding

On Wed, Jun 12, 2013 at 12:22:29AM +0200, Sebastian Hesselbarth wrote:

sorry to kick into this thread that late but Ezequiel made me think of
address windows when asking on IRC. From what I can see from your and
Arnd's proposal the only real difference is that having it Arnd's way
allows you to have two or more windows mapped to e.g. devbus with
totally independent address ranges - while yours requires one large
window for all child devices?

Sorry, I'm having problems following the possessives in your paragraph
- which things are you comparing?

Although, not thought to the bare end this could also work and maybe
reflects the actual hardware more accuate:

I actually posted something like this a time ago, but Arnd's
suggestion to encode the target id in the address seems much clearer,
and more accurate, though a bit more work to parse.

It is 'better' in that the base addresses are in exactly one place -
the ranges of the mbus node. With marvell,mbus-target the base
addreses are strewn everywhere and now are difficult to change.

A main consideration here is that the bootloader needs to update the
base addresses - to support the 0xd0 vs 0xf1 internal-regs base
address issue. So I think that requirement alone is enough to make
marvell,mbus-target undesirable.

When removing size from marvell,mbus-target above, mbus driver could
also probe for required max size from the reg properties of the child
nodes. Arnd already said that mbus isn't "simple-bus" anymore, why
can't it just walk through the nodes and collect required windows?

With enough restrictions, I think it is pretty easy to parse
marvell,mbus-target, but you can employ the same restrictions to
simplify parsing the 2 cell address format too.

Jason