From mboxrd@z Thu Jan 1 00:00:00 1970 Received: with ECARTIS (v1.0.0; list linux-mips); Tue, 27 May 2003 10:26:58 +0100 (BST) Received: from p508B77C3.dip.t-dialin.net ([IPv6:::ffff:80.139.119.195]:22478 "EHLO dea.linux-mips.net") by linux-mips.org with ESMTP id ; Tue, 27 May 2003 10:26:56 +0100 Received: from dea.linux-mips.net (localhost [127.0.0.1]) by dea.linux-mips.net (8.12.8/8.12.8) with ESMTP id h4R9QobY023587; Tue, 27 May 2003 02:26:50 -0700 Received: (from ralf@localhost) by dea.linux-mips.net (8.12.8/8.12.8/Submit) id h4R9QnxQ023586; Tue, 27 May 2003 11:26:49 +0200 Date: Tue, 27 May 2003 11:26:49 +0200 From: Ralf Baechle To: Ashish anand Cc: linux-mips@linux-mips.org Subject: Re: Any complications of using CONFIG_MIPS_UNCACHED..? Message-ID: <20030527092649.GB23296@linux-mips.org> References: <200305210618.h4L6HqI9006634@smtp.inspirtek.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200305210618.h4L6HqI9006634@smtp.inspirtek.com> User-Agent: Mutt/1.4.1i 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: 2455 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 Wed, May 21, 2003 at 11:16:49AM +0530, Ashish anand wrote: > I saw a good bit of discussion about CONFIG_MIPS_UNCACHED but > still i am yet to know... > > If I want to use CONFIG_MIPS_UNCACHED (ignoring performance) > what all the side-effects and any restrictions that linux should > take care in software ? > > I observed something surprising on my R4k mips system(virtually indexed > caches), after i use this option my driver never got status updation by > device in transmit and receive decriptors in system memory , Irrespective > of I (flushed+invalidate) caches or not... Descriptors sounds like networking. Network descriptors should usually be stored in uncached or otherwise coherent space that is allocated through pci_alloc_consistent anyway. If you do that CONFIG_MIPS_UNCACHED should not make any difference anymore. > if i don't use CONFIG_MIPS_UNCACHED then before checking status I need to > (flush+invalidate) cache and whole thing works great... That's a funny bug. Normally the opposite behaviour would be expected for a bug ... Ralf