From mboxrd@z Thu Jan 1 00:00:00 1970 Received: with ECARTIS (v1.0.0; list linux-mips); Mon, 01 Oct 2007 11:59:59 +0100 (BST) Received: from localhost.localdomain ([127.0.0.1]:56012 "EHLO dl5rb.ham-radio-op.net") by ftp.linux-mips.org with ESMTP id S20022280AbXJAK74 (ORCPT ); Mon, 1 Oct 2007 11:59:56 +0100 Received: from denk.linux-mips.net (denk.linux-mips.net [127.0.0.1]) by dl5rb.ham-radio-op.net (8.14.1/8.13.8) with ESMTP id l91AxtPV013546; Mon, 1 Oct 2007 11:59:55 +0100 Received: (from ralf@localhost) by denk.linux-mips.net (8.14.1/8.14.1/Submit) id l91AxsUN013495; Mon, 1 Oct 2007 11:59:54 +0100 Date: Mon, 1 Oct 2007 11:59:54 +0100 From: Ralf Baechle To: veerasena reddy Cc: linux-mips , "linux-kernel.org" Subject: Re: linux cache routines for Write-back cache policy on MIPS24KE Message-ID: <20071001105954.GB23647@linux-mips.org> References: <119374.35234.qm@web8401.mail.in.yahoo.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <119374.35234.qm@web8401.mail.in.yahoo.com> User-Agent: Mutt/1.5.14 (2007-02-12) Return-Path: X-Envelope-To: <"|/home/ecartis/ecartis -s linux-mips"> (uid 0) X-Orcpt: rfc822;linux-mips@linux-mips.org Original-Recipient: rfc822;linux-mips@linux-mips.org X-archive-position: 16760 X-ecartis-version: Ecartis v1.0.0 Sender: linux-mips-bounce@linux-mips.org Errors-to: linux-mips-bounce@linux-mips.org X-original-sender: ralf@linux-mips.org Precedence: bulk X-list: linux-mips On Mon, Oct 01, 2007 at 10:04:32AM +0100, veerasena reddy wrote: > I have ported Linux-2.6.18 kernel on MIPS24KE > processor. I am using write back cache policy. > > Could you please guide me under what cases the below > cache API's are being used: > - dma_cache_wback_inv() : Could you explain what > exactly this function does > - dma_cache_wback() : This function write back the > cache data to memory > - dma_cache_inv : This function invalidate the cache > tags. so subsequent access will fetch from memory. > > Once I looked the above function definitions in > linux-2.6.18/arch/mips/mm/c-r4k.c. > All these function's implemetation are same except > bc_wbak_inv() is called in both dma_cache_wback-inv() > and dma_cache_wback(), where as bc_inv() is called in > case of dma_cache_inv. > > Also, bc_inv()/bc_wbak_inv are define as null > implementation for R4000. > That means all three functions are doing same > functionality in case of R4000. > > What are the difference between these three functions. > Under what cases these functions are used. An internal only interface to be used with I/O cache coherency. > Please guide me if you have any links which will > explain these API's. Easy answer, don't use them, for 2.6.24 I've queued a patch to kill this API. Documentation/DMA-API.txt documents how to properly deal with I/O coherency in Linux. Ralf