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?