From mboxrd@z Thu Jan 1 00:00:00 1970 Received: by oss.sgi.com id ; Wed, 24 Jan 2001 16:58:10 -0800 Received: from deliverator.sgi.com ([204.94.214.10]:46430 "EHLO deliverator.sgi.com") by oss.sgi.com with ESMTP id ; Wed, 24 Jan 2001 16:57:40 -0800 Received: from lappi.waldorf-gmbh.de (dhcp-163-154-5-208.engr.sgi.com [163.154.5.208]) by deliverator.sgi.com (980309.SGI.8.8.8-aspam-6.2/980310.SGI-aspam) via ESMTP id QAA04846 for ; Wed, 24 Jan 2001 16:56:42 -0800 (PST) mail_from (ralf@oss.sgi.com) Received: (ralf@lappi.waldorf-gmbh.de) by bacchus.dhis.org id ; Wed, 24 Jan 2001 16:31:02 -0800 Date: Wed, 24 Jan 2001 16:31:02 -0800 From: Ralf Baechle To: Jun Sun Cc: Pete Popov , Quinn Jensen , linux-mips@oss.sgi.com Subject: Re: CONFIG_MIPS_UNCACHED Message-ID: <20010124163101.F863@bacchus.dhis.org> References: <3A6E132B.9000103@Lineo.COM> <3A6E1977.2B18484D@mvista.com> <3A6F36B8.4F10759B@mvista.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5i In-Reply-To: <3A6F36B8.4F10759B@mvista.com>; from jsun@mvista.com on Wed, Jan 24, 2001 at 12:10:32PM -0800 X-Accept-Language: de,en,fr Sender: owner-linux-mips@oss.sgi.com Precedence: bulk Return-Path: X-Orcpt: rfc822;linux-mips-outgoing On Wed, Jan 24, 2001 at 12:10:32PM -0800, Jun Sun wrote: > It is really surprising to know this. It sounds like a CPU bug to me. Can > some MIPS "gods" clarify if such a behaviour is a bug or allowed? > > BTW, the CPU in EV96100 is QED RM7000, I believe. If you want to be strictly correct you have to execute the code that disables caching of KSEG0 in uncached space like KSEG1, then flush the caches before you can resume execution in KSEG0. Otherwise you might end up with dirty d-caches which when flushed will overwrite more uptodate data in memory. The window is very small but yet exists if things are just right. Ralf