On Wed, 2011-03-23 at 14:54 +0100, Arend van Spriel wrote:
> On Wed, 23 Mar 2011 14:49:43 +0100, Michael BÃsch <mb@xxxxxxxxx> wrote:
>
> >
> >> void foobar(void *r, u32 val)
> >> {
> >> volatile u32 dummy;
> >>
> >> WR_REG(r, val);
> >> dummy = RD_REG(r);
> >> }
> >>
> >> The register read is necessary to assure the register write is properly
> >> flushed out in hardware. Could removing the volatile for the dummy
> >> variable cause removal of the register read due to code optimization.
> >
> > It shouldn't optimize the read away as long as the RD_REG uses a
> > volatile pointer internally. Which is the case if you use readl/w/b or
> > ioread... to implement RD_REG
>
> Well, RD_REG(r) is a macro which translates to readb((volatile u8*)r). Are
> you referring to that being a volatile pointer or do you mean that inside
> the accessor function readb the 'r' parameter is treated as a volatile
> pointer.
readb uses volatile internally. That should be enough to ensure that
the read does actually happen.
--
Greetings Michael.
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