On Mar 31, 2010, at 7:45 AM, 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?
bus_space_barrier() doesn't flush ... barriers only enforce the ordering of
operations (and, of course, with respect to non-overlapping addresses ...
obviously reads after writes of the same address in code will be enforced on
the bus without an explicit barrier).
>
> Dave
>
> --
> David Young OJC Technologies
> dyo...@ojctech.com Urbana, IL * (217) 278-3933
-- thorpej
