On Thu, 14 May 2009 23:35:36 -0600 (MDT) "M. Warner Losh" <i...@bsdimp.com> mentioned:
> In message: <20090515092205.6f6d06fa.s...@freebsd.org> > Stanislav Sedov <s...@freebsd.org> writes: > : On Thu, 14 May 2009 21:37:12 -0600 (MDT) > : "M. Warner Losh" <i...@bsdimp.com> mentioned: > : > : > In message: <200905122114.n4cleag9033...@svn.freebsd.org> > : > Stanislav Sedov <s...@freebsd.org> writes: > : > : @@ -926,6 +937,7 @@ atestart_locked(struct ifnet *ifp) > : > : * tell the hardware to xmit the packet. > : > : */ > : > : WR4(sc, ETH_TAR, segs[0].ds_addr); > : > : + BARRIER(sc, ETH_TAR, 8, BUS_SPACE_BARRIER_WRITE); > : > : WR4(sc, ETH_TCR, segs[0].ds_len); > : > > : > Why is a barrier needed here? > : > > : Writing the TCR register triggers the transmit, so it had to be written > : strongly after the TAR register. That's why I added the barrier here. > > Then shouldn't the barrier be after TCR write? Or does this ensure > that the write is before TCR? > Yeah, this barrier is to ensure that the TCR register gets written after the TAR register has been written, not before. I don't think an additional barrier is needed after the TCR write. -- Stanislav Sedov ST4096-RIPE !DSPAM:4a0d7945994291484520249! _______________________________________________ svn-src-all@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/svn-src-all To unsubscribe, send any mail to "svn-src-all-unsubscr...@freebsd.org"
