Re: [PATCH] TX49 MFC0 bug workaround

[Sergei Shtylylov <sshtylyov@ru.mvista.com>]

Hello.

Ralf Baechle wrote:

> > > Workaround: mask EXL bit of the result or place a nop before mfc0.
> > [...]
> >
> > > @@ -55,8 +56,13 @@ __asm__ (
> > >         "  di                                                      \n"
> > > #else
> > >         "  mfc0    $1,$12                                          \n"
> > > +#if TX49XX_MFC0_WAR && defined(MODULE)
> > > +       "  ori     $1,3                                            \n"
> > > +       "  xori    $1,3                                            \n"
> > > +#else
> > >         "  ori     $1,1                                            \n"
> > >         "  xori    $1,1                                            \n"
> > > +#endif
> > >         "  .set    noreorder                                       \n"
> > >         "  mtc0    $1,$12                                          \n"
> > > #endif
> > Hmm, wouldn't that "nop" alternative be simpler?
> Simpler maybe - but this variant has zero runtime overhead.
   And.. how do you imagine placing a NOP (which surely just moves MFC0 down 
so that it's a 1st insn. on the next page). What if it'll move it to the 
errata prone address from a safe one instead?
WBR, Sergei