From mboxrd@z Thu Jan 1 00:00:00 1970 From: Segher Boessenkool Subject: Re: [PATCH v2] gianfar: Add I/O barriers when touching buffer descriptor ownership. Date: Thu, 3 May 2007 01:42:06 +0200 Message-ID: <9403063bda028d0dfe9e5a05ceea4d7a@kernel.crashing.org> References: <20070502195712.GA16541@ld0162-tx32.am.freescale.net> <4638F0C4.2000406@freescale.com> <4638F734.2040809@freescale.com> Mime-Version: 1.0 (Apple Message framework v623) Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: linuxppc-dev@ozlabs.org, jgarzik@pobox.com, netdev@vger.kernel.org To: Scott Wood Return-path: In-Reply-To: <4638F734.2040809@freescale.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linuxppc-dev-bounces+glppd-linuxppc64-dev=m.gmane.org@ozlabs.org Errors-To: linuxppc-dev-bounces+glppd-linuxppc64-dev=m.gmane.org@ozlabs.org List-Id: netdev.vger.kernel.org >>> And the driver is already ppc-specific; it uses in/out_be32. >> >> True, but its hidden behind the gfar_read/write accessors. >> >> Your change is a bit more blatant. > > Well, Segher doesn't want me to use iobarrier (because it's not I/O). > Andy doesn't want me to use wmb() (because it's sync). You should use wmb(), but unfortunately too strong semantics are required for that (ordering wrt I/O) so it's a full sync on PowerPC. I don't believe a priori that that would be notably slower, but if actually is, you could use eieio() I suppose since you say the driver is powerpc specific -- but please put a comment in the source code then saying why you don't use wmb() there. Segher