From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from oxtel.com (mail.oxtel.com [193.200.114.15]) by bilbo.ozlabs.org (Postfix) with ESMTP id 043FCB7067 for ; Thu, 3 Sep 2009 18:15:15 +1000 (EST) Message-ID: <4A9F78AF.4010206@oxtel.com> Date: Thu, 03 Sep 2009 09:05:03 +0100 From: Chris Pringle MIME-Version: 1.0 To: azilkie@datacast.com Subject: Re: AW: PowerPC PCI DMA issues (prefetch/coherency?) References: <1251926572.10090.17.camel@Adam> In-Reply-To: <1251926572.10090.17.camel@Adam> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Cc: Tom Burns , Andrea Zypchen , linuxppc-dev@lists.ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Hi Adam, If you have a look in include/asm-ppc/pgtable.h for the following section: #ifdef CONFIG_44x #define _PAGE_BASE (_PAGE_PRESENT | _PAGE_ACCESSED | _PAGE_GUARDED) #else #define _PAGE_BASE (_PAGE_PRESENT | _PAGE_ACCESSED) #endif Try adding _PAGE_COHERENT to the appropriate line above and see if that fixes your issue - this causes the 'M' bit to be set on the page which sure enforce cache coherency. If it doesn't, you'll need to check the 'M' bit isn't being masked out in head_44x.S (it was originally masked out on arch/powerpc, but was fixed in later kernels when the cache coherency issues with non-SMP systems were resolved). The patch I had fixed two problems on 2.6.26 for 'powerpc': 1) It stopped the 'M' bit being masked out (head_32.S) 2) It set the cache coherency ('M' bit) flag on each page table entry (pgtable-ppc32.h) Hope this helps! Cheers, Chris Adam Zilkie wrote: > Hi Chris, > > I am having a problem similar to what you described in this discussion. > We are using the ppc arch with 2.6.24 with CONFIG_SEQUOIA with compiles > arch/ppc/kernel/head_44x.c (quite different > from /arch/powerpc/kernel/head_32.S). I would like to apply your > backporting patch to this architecture. Any help would be appreciated. > > Regards, > Adam > > -- ______________________________ Chris Pringle Software Design Engineer Miranda Technologies Ltd. Hithercroft Road Wallingford Oxfordshire OX10 9DG UK Tel. +44 1491 820206 Fax. +44 1491 820001 www.miranda.com ____________________________ Miranda Technologies Limited Registered in England and Wales CN 02017053 Registered Office: James House, Mere Park, Dedmere Road, Marlow, Bucks, SL7 1FJ