[U-Boot] [PATCH 8/9] mpc8641: Change 32-bit memory map

Becky Bruce
2008-11-06T22:12:17Z

On Nov 6, 2008, at 1:28 PM, Scott Wood wrote:

> Becky Bruce wrote:
>> The memory map on the 8641hpcn is modified to look more like
>> the 85xx boards; this is a step towards a more standardized
>> layout going forward. As part of this change, we now relocate
>> the flash.
>> The regions for some of the mappings were far larger than they
>> needed to be. I have reduced the mappings to match the
>> actual sizes supported by the hardware.
>
> Was this causing any actual problems? It seems to be inviting
> gratuitous breakage if the device tree isn't updated at the same
> time, or for any OSes not using the device tree.
>

Was it causing any problems for anybody running it? Only minor
stuff. Was it causing maintenance to be a god-awful nightmare?
Definitely. The map for 86xx was a real mess, and really needed to be
cleaned up - trying to make sense of the previous code was a real
pain, and the whole structure of it was very fragile - any attempt to
make a change resulted in random breakage because it was such a house
of cards (which I ran into repeatedly while doing the 36b stuff). The
decision to change the map was also made for ease of code maintenance
- having a similar map to 85xx makes it much easier now to port the
36b changes over to that platform which is the next major task. The
boot sequences for the 2 platforms are also a lot more similar now, so
I'm hoping that a little bit of pain now will save us a lot more pain
in the future.

I agree that there's potential for breakage, but in the case of Linux,
which is the vast majority of u-boot users, I think it's minimal. For
the non-linux cases, changing an OS to accomodate the new map should
be a minor task.

The device tree changes are in hand, and as soon as this goes into the
u-boot tree, I will push those to Linux.

We *do* need a comment in the release notes for this revision of u-
boot that the map for 8641 has changed so it doesn't catch anyone by
surprise.

-B