From mboxrd@z Thu Jan 1 00:00:00 1970 Received: with ECARTIS (v1.0.0; list linux-mips); Mon, 03 Oct 2005 14:16:10 +0100 (BST) Received: from nevyn.them.org ([66.93.172.17]:683 "EHLO nevyn.them.org") by ftp.linux-mips.org with ESMTP id S3465648AbVJCNPy (ORCPT ); Mon, 3 Oct 2005 14:15:54 +0100 Received: from drow by nevyn.them.org with local (Exim 4.52) id 1EMQAa-0004y2-EJ; Mon, 03 Oct 2005 09:15:52 -0400 Date: Mon, 3 Oct 2005 09:15:52 -0400 From: Daniel Jacobowitz To: Ralf Baechle Cc: "Maciej W. Rozycki" , Andrew Isaacson , linux-mips@linux-mips.org Subject: Re: [patch 1/5] SiByte fixes for 2.6.12 Message-ID: <20051003131551.GA19075@nevyn.them.org> References: <20050622230042.GA17919@broadcom.com> <20051001092807.GD14463@linux-mips.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20051001092807.GD14463@linux-mips.org> User-Agent: Mutt/1.5.8i 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: 9121 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: dan@debian.org Precedence: bulk X-list: linux-mips On Sat, Oct 01, 2005 at 10:28:07AM +0100, Ralf Baechle wrote: > On Thu, Jun 23, 2005 at 12:01:57PM +0100, Maciej W. Rozycki wrote: > > > Well, the flag is not really to specify whether the common code is to be > > used or not. It's about whether the TLB is like that of the R4k. > > Actually it's always been a mystery for me why the common code cannot be > > used for the SB1, but perhaps there is something specific that I could > > only discover in that "SB-1 Core User Manual" that I yet have to see, > > sigh... > > > > Of course if your TLB is indeed different from that of the R4k, then you > > shouldn't be setting cp0.config.mt to 1 in the first place... > > The reason was primarily the tiny bit of extra performance because the > SB1 doesn't need the hazard handling overhead. Also tlb-sb1 has a few > changes that are needed to initialize a TLB in undefined state after > powerup. That was needed to run Linux on firmware-less SB1 cores. FYI, all I have is a piece of hard evidence: this patch was the difference between not booting and booting for a Sentosa with CFE. Which isn't firmwareless and isn't a tiny bit of extra performance issue. I'll try to give CVS HEAD a shot this week sometime. -- Daniel Jacobowitz CodeSourcery, LLC