svn commit: r192027 - head/sys/arm/at91

[M. Warner Losh]

In message: <20090515092205.6f6d06fa.stas at FreeBSD.org>
            Stanislav Sedov <stas at FreeBSD.org> writes:
: On Thu, 14 May 2009 21:37:12 -0600 (MDT)
: "M. Warner Losh" <imp at bsdimp.com> mentioned:
: 
: > In message: <200905122114.n4CLEag9033208 at svn.freebsd.org>
: >             Stanislav Sedov <stas at 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?

Warner