Re: CVS commit: src/sys/dev/ic

[Andrew Doran <ad%NetBSD.org@localhost>]

On Wed, Mar 31, 2010 at 09:45:40AM -0500, David Young wrote:
> On Wed, Mar 31, 2010 at 05:09:41AM +0000, Michael Lorenz wrote:
> > Module Name:        src
> > Committed By:       macallan
> > Date:               Wed Mar 31 05:09:41 UTC 2010
> > 
> > Modified Files:
> >     src/sys/dev/ic: pcf8584.c
> > 
> > Log Message:
> > Do as OpenSolaris does and read the status register after each write.
> > Now this driver works on my Blade 2500.
> 
>  void
>  pcfiic_write(struct pcfiic_softc *sc, bus_size_t r, u_int8_t v)
>  {
> +       volatile uint8_t junk;
>         bus_space_write_1(sc->sc_iot, sc->sc_ioh, sc->sc_regmap[r], v);
> +       junk = bus_space_read_1(sc->sc_iot, sc->sc_ioh, PCF_S1);
>         bus_space_barrier(sc->sc_iot, sc->sc_ioh, sc->sc_regmap[r], 1,
>             BUS_SPACE_BARRIER_WRITE);
>  }
> 
> I wonder, does the device need the read, or is the bus_space_barrier()
> insufficient to flush the write to the device?

Additionally, should this read not be after the barrier?