[U-Boot] [u-boot-release] [PATCH] [v3] p1022ds: use weak CFI flash accessorswhen DIU is enabled

[Scott Wood]

On Thu, 16 Sep 2010 19:51:33 -0700
Tabi Timur-B04825 <B04825 at freescale.com> wrote:

> Jaggi Manish-B10520 wrote:
> > Most of the read/write functions do this way
> > 0:+       int sw = set_mux_to_lbc();
> > 1:+
> > 2:+       ret = __raw_readl(addr);
> > 3:+       if (sw)
> > 4:+               set_mux_to_diu();
> >
> > compiler might reorder 2 before 3 and 0, read / write wont have any
> > issue , right ?
> 
> Really?  I don't see why the compiler would do that.  That would be a bug, IMHO.

Only if set_mux_to_lbc() is non-inline, and the compiler has no
visibility into what it does.

But even then, the hardware is free to reorder.  That's why we have
non-raw I/O accessors.

> Can you explain why you think it will make such a reordering?  My 
> understanding is that the compiler reorders things that don't have any side 
> effects.

The compiler can reorder anything where the reordering won't affect the
results of single-threaded execution with no interrupts,
well-behaved memory (no device registers, bank switches, etc), no
violations of aliasing rules, etc.

-Scott