how do i add the defn for the beagle xM to barebox?

[Sascha Hauer]

On Sun, Feb 05, 2012 at 04:04:07PM -0500, Robert P. J. Day wrote:
> On Sun, 5 Feb 2012, Eric Bénard wrote:
> 
> > Le Sun, 5 Feb 2012 13:00:13 -0500 (EST),
> > "Robert P. J. Day" <rpjday at crashcourse.ca> a écrit :
> >
> > > On Sun, 5 Feb 2012, Eric Bénard wrote:
> > >
> > > > This is the case where u-boot is built with SPL thus reoplacing
> > > > x-load : they always read NAND ID as some XM boards were mounted
> > > > with Numonyx POP which includes NAND and 166MHz RAM when mot XM
> > > > boards have a POP with only 200MHz DDR (and in that case
> > > > manufacturer ID is 0). So even on a XM you need to check the NAND ID
> > > > to set the right RAM settings.
> > >
> > >   ah, got it.  but what about in a more general case?  what if you
> > > have a current, accurate definition for an existing board?  then a
> > > *slight* variant of that board comes along, for which some settings in
> > > the defconfig file are simply wrong?
> > >
> > >   are there any examples of that in barebox right now?  and if not,
> > > how would one handle them?  put another way, what if *all* xM boards
> > > had no NAND?  then we'd be back to my original question, and it's
> > > still not clear how you'd define that new board for barebox.
> > >
> > if no XM board had NAND, you would simply check the board type using the
> > GPIO sampled and you wouldn't register the nand (line 305 in
> > board-beagle.c) and the fact that the nand driver is enabled is not a
> > problem if the device is not registrered the driver won't be used.
> 
>   not to put too fine a point on it but ... yuck.  don't get me wrong,
> i certainly see the value in testing things like board versions so the
> code knows how to handle small differences between similar boards
> (memory speed, flash types or sizes and so on).
> 
>   but this isn't a small difference -- this represents potentially an
> entire subsystem (NAND) that i want the ability to de-activate.  in a
> perfect world, i want the ability to say concisely that i have a
> beagle but i have no NAND flash, period.  i don't want any of the NAND
> code compiled, i don't want it included in the binary, so obviously i
> don't want any of that code to run, only to realize it has nothing to
> do.

The mentioned U-Boot code does not use any of the nand layer but only
some omap specific function to detect the nand id (identify_nand_chip).
This means that you can add this code to barebox and still disable nand
support.

If you still want to have a more fine grained config we can add a

config MACH_PANDA_XM_VARIANT
	bool

config MACH_PANDA_XM_DETECT_RAM_TYPE
	bool

But we should add such options with care. Generally I don't really
like to ask the user complicated questions for things that can be
autodetected.

Sascha

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