Subject: Re: [PATCH] add restart function for mpc52xx

From: Benjamin Herrenschmidt <[email-masked]>
Date: Mon, 29 Jan 2007 08:48:30 +1100

> Look how rmk has solved it for ARM - Sascha has already described it.
> The code that gets the information "this is an xyz board" knows
> _everything_, starting from the CPU type, up to which peripherals are
> there. So it simply can spawn the right platform devices, apply bugfixes
> to everything a board vendor has never thought of and is even unwilling
> to change in the future, because he simply doesn't care.
> 
> It's not that ARM is different than today's SoC PowerPC processors. It's
> just that the arm-linux people solved the problems you are describing
> here years ago.

Can we setup a filter on this mailing list rejecting anybody comparing
ARM to PowerPC -again- ? I'm tired of those useless rants.

Of course, the device-tree isn't there to solve world hunger and we
don't require people to constantly change their firmwares. Yes, a few
people on this list are probably attempting to "abuse" it and do some
kind of magic uber-board support that does everything and more and I
don't agree with that approach.

However it's actually quite nice and useful to have a well defined
firmware binding for common devices and things like interrupt routing. 

You might notice that the minimum device-tree as defined by the spec is
actually fairly small... only a couple of nodes & properties. One of
these is ... a board name. Which in a way is equivalent to your ARM
board number (except that we prefer ASCII strings to magic numbers here
is ppc land). From that is generally derived the board support data
structure.

The board code is then in total control, just like ARM or whoever else
you seem to like much better. Then, for various "services", like PCI,
interrupt routing, etc... we provide a way to easily define the whole
thing via the device-tree and the code "just works". Cool no ? Well, of
course, you -STILL- have the possibility of not using that for most
things, and to fix it up when it's wrong. You don't =have= to update the
firmware (heh, like if I had any chance to get Apple to fix their
firmwares when they have bugs).

So we are providing something that is a superset of the board number you
seem to like that much, adding more flexibility...

Anyway, enough of that. Either be constructive or return to
linuxppc-embeded.

Ben.