[U-Boot] [PATCH V2] i.MX28: Drop __naked function from spl_mem_init

[Marek Vasut]

Dear Wolfgang Denk,

> Dear Stefano,
> 
> In message <4F683862.4030709 at denx.de> you wrote:
> > > +	/* The following is "subs pc, r14, #4", used as return from DABT. */
> > > +	const uint32_t data_abort_memdetect_handler = 0xe25ef004;
> 
> ...
> 
> > Are we maybe becoming warning addicted ? I know the reason for this (GCC
> > raises a warning "-fstack-usage not supported for this target"), you
> > have already asked the gcc people about this issue, and I do not have an
> > idea how to fix this warning in a different way as you did. This is a
> > sort of self-modifying code.
> 
> In which way is this self-modifying code? I don't think so.

Because it rewrites piece of RAM, which is then called in the Data abort 
context.
> 
> > However, the original code is quite easy to understand - I cannot say
> > the same after the patch, we rely on the comment to understand something.
> 
> That's what comments are made for :-)
> 
> > Should we really fix such as warnings even if we generate some obscured
> > code ? Wolfgang, what do you think about ?
> 
> Yes, we should fix warnings.  If you run a MAKEALL and can be sure
> that any message printed is a new problem you will not miss it, and
> act as needed.  If youy know that a build will pop up a number or
> warnings, it's all too easy to miss if there is a new one - and
> checking takes much more concentration.  This is to be avoided.
> 
> On the other hand, I agree that we should avoid obscure code as
> well.  But then, to me the assembler code "subs pc, r14, #4" is
> already obscure enough - I have to admit that I don't really grok it,
> nor why this needs to be a __naked function.

What it does: return from abort mode back from where it was aborted, one 
instruction further.
Why is it naked: Because you don't want to generate prelude etc. only the real 
contents of the function. That gives exactly 4 bytes. And that's what is used to 
rewrite the DABT handler.
> 
> My understanding is that to avoid the warning we can either use this
> "pre-compiled constant instruction" trick, or we would have to create
> a new assembler source file for this single instruction function.

Or put it into start.S

> 
> When Marek and I discussed this, the constant seemed to be the
> simplest approach (not the nicest, though).

Ack
> 
> If you don't like it, then we I think we will end up with a new tiny
> assembler source file.  Would that be preferred by you?
> 
> Best regards,
> 
> Wolfgang Denk

Best regards,
Marek Vasut