Subject: Re: USB support on mpc5200 broken

From: Peter Korsgaard <[email-masked]>
Date: Mon, 29 Sep 2008 19:05:34 +0200

>>>>> "Sven" == Sven Luther <[email-masked]> writes:

Hi,

 >> This, of course, is exactly why I *don't* recommend embedded platforms
 >> move to including the device tree in the flashed firmware.  Keeping
 >> the device tree in the bootwrapper means that it *is* updated with the
 >> kernel and we don't have to mess around with as much backwards
 >> compatibility junk.

 Sven> This completely defeats the purpopse of having a separate
 Sven> device tree though, no ? I mean, we could just as well hardcode
 Sven> the device-tree info in the kernel in this case ?

Well, yes and no. The device tree brings a number of advantages (and a
few disadvantages as well), one of those being the potential
decoupling of kernel and DT. Even if you don't make use of that
feature in a production build you still have the other advantages
(E.G. easy compile test of multiple boards, limited
repeated-these-are-my-platform-devices code in board files, ...).

 Sven> (In embedded cases, the kernel is usyually in the flash as
 Sven> well, so you just upgrade both at the same time :)

Sure, but if you do that you might as well include them in a single
uImage because:

- They are always in sync
- You don't waste flash space (E.G. the DT is very small, but you
  waste a complete flash sector)

With uImage.<platform> U-Boot can still fix up the tree before booting
the kernel, so you don't lose any functionality (E.G. if you
enable/disable certain nodes based on what option boards are
available).

-- 
Bye, Peter Korsgaard