Re: [PATCH] [PowerPC] MPC8272ADS: fix device tree for 8 MB flash, size

[Scott Wood <scottwood@freescale.com>]

On Fri, May 15, 2009 at 07:54:51AM +0200, Heiko Schocher wrote:
> Scott Wood wrote:
> > We should proabbly leave out the ranges altogether, and have u-boot
> > populate it from the mappings it establishes.
> 
> No, I vote for manipulating just the entries, which u-boot dynamically
> detect, and let the other entries untouched. It is possible that
> there is a device which u-boot didn;t use/know, and there is in the DTS
> an ranges entry for it (Maybe not on the MPC8727ADS, but we should
> define a rule, how a bootloader has to manipulate entries). So if
> u-boot build the complete ranges entry, it maybe miss something.

If u-boot doesn't know about it, then it didn't create the mapping, and
thus it's not accessible (if something later on creates a mapping, it can
update ranges itself).  The devices themselves would still be described,
just not the non-existent mapping.

The benefit is that you would have just one place that reads out the
localbus config into the device tree, with no error-prone duplication of
data, or separate hacks for each board that has something that is
variable.

We could leave ranges in the dts for cuImage, and have u-boot just
overwrite the entire thing rather than patch up individual entries.

> > I don't see how current u-boot would accomodate more than 8MiB flash on
> > this board (there's some detection in board/freescale/mpc8260ads/flash.c,
> 
> Didn;t this board uses the CFI driver? :-(

Not yet, unfortunately.  This is pretty old code.

-Scott