Hi, On Thu, Oct 13, 2011 at 5:54 PM, YongHyeon PYUN <pyu...@gmail.com> wrote: > On Thu, Oct 13, 2011 at 05:02:58PM -0400, Arnaud Lacombe wrote: >> Hi, >> >> On Thu, Oct 13, 2011 at 4:47 PM, YongHyeon PYUN <pyu...@gmail.com> wrote: >> > On Thu, Oct 13, 2011 at 12:59:35AM -0700, per...@pluto.rain.com wrote: >> >> YongHyeon PYUN <pyu...@gmail.com> wrote: >> >> > On Wed, Oct 12, 2011 at 10:07:02AM -0400, Karim wrote: >> >> > > ... why are we ORing the same call twice isn't the same thing >> >> > > as calling it once: >> >> > > >> >> > > bmsr = PHY_READ(sc, E1000_SR) | PHY_READ(sc, E1000_SR); >> >> > >> >> > The E1000_SR_LINK_STATUS bit is latched low so it should be read >> >> > twice. >> >> >> >> It might not be a bad idea to check the generated code to be sure >> >> that the read _is_ being done twice. ?An optimizer might well come >> >> to the same conclusion as Karim, and discard the "redundant" second >> >> instance (unless there's a "volatile" declaration somewhere in the >> >> expansion of PHY_READ, to explicitly indicate that it has side >> >> effects). >> > >> > Last time I checked it, compiler generated correct code. >> > Tried again on amd64 and I can still see the code is there. >> > >> What about other architecture (especially i386) ? which optimization > > Don't use i386 so I don't know. > >> level did you use ? which compiler version ? > > CURRENT, default optimization(O2). > >> >> About the last question, I know for sure that there has been change in >> FreeBSD's gcc between 7-STABLE, and FreeBSD -CURRENT. >> >> I agree with perryh@ than such hardware requirement _requires_ being >> explicit in the code, ie proper `volatile' marking. >> > > I'm not saying adding more safe belt is bad idea. If you have a > patch please submit it. I don't like touching every PHY drivers. > Actually, it should not be needed, the generic implementation of PHY_READREG() is doing an MIIBUS_READREG() which is forwarded to the parent (miibusN here), then its parent (msk(4)).
my bad, - Arnaud >> - Arnaud >> > _______________________________________________ freebsd-net@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-net To unsubscribe, send any mail to "freebsd-net-unsubscr...@freebsd.org"
