[U-Boot] GCC 5.2 issue on imx28

[Jörg Krause]

On Mi, 2015-08-05 at 20:23 +0100, Måns Rullgård wrote:
> Jörg Krause <joerg.krause at embedded.rocks> writes:
> 
> > Dear Måns Rullgård, Otavio Salvador,
> > 
> > On Di, 2015-07-28 at 14:39 +0100, Måns Rullgård wrote:
> > > Otavio Salvador <otavio.salvador at ossystems.com.br> writes:
> > 
> > [snip]
> > 
> > > There are two errors reports:
> > > 
> > > 1. An undefined reference to the symbol "lowlevel_init"
> > > 2. A complaint about the ".rel.plt" section not being handled by 
> > > the
> > >    linker script.
> > > 
> > > The second error is probably caused by the first.  A quick grep 
> > > turns 
> > > up
> > > this snippet in arch/arm/cpu/arm926ejs/mxs/mxs.c:
> > > 
> > > /* Lowlevel init isn't used on i.MX28, so just have a dummy here 
> > > */
> > > inline void lowlevel_init(void) {}
> > > 
> > > The semantics for non-static functions declared inline have 
> > > changed 
> > > in
> > > gcc5, causing the above (empty) function not to be emitted as an
> > > external symbol.
> > > 
> > > Since that function is only referenced from start.S, it should 
> > > not be
> > > declared inline at all.  This patch should thus fix your problem:
> > > 
> > > diff --git a/arch/arm/cpu/arm926ejs/mxs/mxs.c 
> > > b/arch/arm/cpu/arm926ejs/mxs/mxs.c
> > > index ef130ae..b1d8721 100644
> > > --- a/arch/arm/cpu/arm926ejs/mxs/mxs.c
> > > +++ b/arch/arm/cpu/arm926ejs/mxs/mxs.c
> > > @@ -24,7 +24,7 @@
> > >  DECLARE_GLOBAL_DATA_PTR;
> > >  
> > >  /* Lowlevel init isn't used on i.MX28, so just have a dummy here 
> > > */
> > > -inline void lowlevel_init(void) {}
> > > +void lowlevel_init(void) {}
> > >  
> > >  void reset_cpu(ulong ignored) __attribute__((noreturn));
> > >  
> > 
> > I stumbled over the same problem. Unfortunatly, I did not find this
> > patch before (only the error report from Otavia) and submitted a
> > similar patch [1] which keeps the inline keyword.
> > 
> > Best regards
> > Jörg Krause
> > 
> > [1] "arm: mxs: make inline function compatible for GCC 5"
> > https://patchwork.ozlabs.org/patch/504043/
> 
> Since the function is only referenced from outside the C file, any 
> use
> of inline makes little sense to me.  While your patch achieves the
> result of creating a linkable instance of the function, it is more
> complicated than it needs to be.
> 

In my opinion it quite make sense to use inline for functions
referenced only from other files. The keyword is just an hint to the
compiler and why should it not make sense for other C files? However,
in this case it makes really no difference if lowlevel_init is marked
as inline, gcc will generate an "BL lowlevel_init" instruction in both
cases.

Jörg