From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from vmx55.multikabel.net (vmx55.multikabel.net [212.127.254.145]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTP id 7D53667A3A for ; Fri, 2 Jun 2006 22:51:56 +1000 (EST) Received: from vmx30.multikabel.net ([212.127.254.138]) by vmx55.multikabel.net with esmtp (Exim 4.44) id 1Fm91M-0001Ll-Kp for linuxppc-dev@ozlabs.org; Fri, 02 Jun 2006 14:44:56 +0200 In-Reply-To: <20060602040426.GA28528@pb15.lixom.net> References: <20060602040426.GA28528@pb15.lixom.net> Mime-Version: 1.0 (Apple Message framework v623) Content-Type: text/plain; charset=US-ASCII; format=flowed Message-Id: <61e1e9d0ada7e9648b8590cfac2b67b9@kernel.crashing.org> From: Segher Boessenkool Subject: Re: [PATCH] [2.6.18] U4 DART improvements Date: Fri, 2 Jun 2006 14:44:50 +0200 To: Olof Johansson Cc: linuxppc-dev@ozlabs.org, paulus@samba.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Hi Olof, Looks good. One request: > +static inline void dart_tlb_invalidate_one(unsigned long bus_rpn) > +{ > + unsigned int reg; > + unsigned int l, limit; > + > + reg = DART_CNTL_U4_ENABLE | DART_CNTL_U4_IONE | > + (bus_rpn & DART_CNTL_U4_IONE_MASK); > + DART_OUT(DART_CNTL, reg); > + mb(); Could you please comment the memory barriers, to say exactly _why_ a certain barrier is needed? I can't see why wmb() wouldn't work here, for example (note I'm not saying it would -- I just don't see why it wouldn't). Same goes for every single memory barrier in the whole kernel source code, but I have to start somewhere, heh. Segher