[PATCH] arm/imx: use Kconfig choice for low-level debug UART selection

[Russell King - ARM Linux]

On Fri, Aug 19, 2011 at 01:39:37PM +0200, Sascha Hauer wrote:
> On Fri, Aug 19, 2011 at 12:09:41PM +0100, Will Deacon wrote:
> > Sascha,
> > 
> > On Fri, Aug 19, 2011 at 07:35:33AM +0100, Sascha Hauer wrote:
> > > On Fri, Aug 19, 2011 at 12:56:59PM +0800, Shawn Guo wrote:
> > > > Now that the DEBUG_LL UART can be selected by a Kconfig choice,
> > > > simplify the #ifdefery in debug-macro.S and add entries to the
> > > > top-level Kconfig.debug instead.
> > > 
> > > I'm unsure whether I like this. The ifdeffery does not look very good,
> > > but the Kconfig snippet is not shorter, also it is in generic arm code
> > > and not i.MX specific. The old way also makes sure that we do not
> > > compile in incompatible lowlevel debug code.
> > 
> > But it's an unfortunate hinderence to a single zImage kernel which we can
> > only solve sensibly in the generic ARM code.
> 
> My problem is that if this option is enabled the kernel will not run
> on any other SoC except the one being selected here, at least when
> earlyprintk is passed on the command line.

I never liked the idea of coupling this into earlyprintk - and I think
I said so at the time.  I'll say it again:

The LL DEBUG stuff is there to be able to do low level "it won't boot"
debugging.  It's not there as a user option.  You are supposed to know
exactly what you are doing when using the option.

If we're going to start having earlyprintk be an argument against this,
I'll simply rip out the earlyprintk coupling to LL debug, and people
can go back to patching printk.c to make this work.

> One could argue
> that this option is for people who exactly know what they do only.

It _IS_ there for people who know what they're doing.  That's something
I keep on saying about the LL debug stuff.  It's there to allow people
to debug the early startup of the kernel.  It's not there for users.