From mboxrd@z Thu Jan 1 00:00:00 1970 Received: with ECARTIS (v1.0.0; list linux-mips); Fri, 24 Dec 2010 13:32:42 +0100 (CET) Received: from gateway13.websitewelcome.com ([69.41.255.6]:56427 "HELO gateway13.websitewelcome.com" rhost-flags-OK-OK-OK-OK) by eddie.linux-mips.org with SMTP id S1491041Ab0LXMcj (ORCPT ); Fri, 24 Dec 2010 13:32:39 +0100 Received: (qmail 14377 invoked from network); 24 Dec 2010 12:31:44 -0000 Received: from gator750.hostgator.com (174.132.194.2) by gateway13.websitewelcome.com with SMTP; 24 Dec 2010 12:31:44 -0000 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=default; d=paralogos.com; h=Received:Message-ID:Date:From:User-Agent:MIME-Version:To:CC:Subject:References:In-Reply-To:Content-Type:Content-Transfer-Encoding:X-Source:X-Source-Args:X-Source-Dir; b=bMCOdYk+LNHyzC9RtW5zbZbr0GPD9jzkvQ3bFM03X3NiuySiszFgtkEykgYD846rPzka34FR4+jWx18YlZFf7Qw6XziE2NeVZf28aqV4Q5L+boBHtPwzeieaVgSoa19P; Received: from [74.125.122.49] (port=10059 helo=kkissell-macbookpro.local) by gator750.hostgator.com with esmtpsa (TLSv1:AES256-SHA:256) (Exim 4.69) (envelope-from ) id 1PW6oz-00068p-TP; Fri, 24 Dec 2010 06:32:34 -0600 Message-ID: <4D1492E0.5090407@paralogos.com> Date: Fri, 24 Dec 2010 04:32:32 -0800 From: "Kevin D. Kissell" User-Agent: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.5; en-US; rv:1.9.2.13) Gecko/20101207 Thunderbird/3.1.7 MIME-Version: 1.0 To: STUART VENTERS CC: "Anoop P.A." , linux-mips@linux-mips.org, Anoop P A Subject: Re: SMTC support status in latest git head. References: <8F242B230AD6474C8E7815DE0B4982D7179FB88D@EXV1.corp.adtran.com> In-Reply-To: <8F242B230AD6474C8E7815DE0B4982D7179FB88D@EXV1.corp.adtran.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - gator750.hostgator.com X-AntiAbuse: Original Domain - linux-mips.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - paralogos.com X-Source: X-Source-Args: X-Source-Dir: 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: 28711 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: kevink@paralogos.com Precedence: bulk X-list: linux-mips Thank you, Stuart! I've spotted some definite breakage to SMTC between those versions. In arch/mips/include/asm/stackframe.h, someone moved the store of the Status register value in SAVE_SOME (line 169 or 204, depending on the version) from two instructions after the mfc0 to a point after the #ifdef for SMTC, presumably to get better pipelining of the register access. Unfortunately, the v1 register is also used in the SMTC-specific fragment to save TCStatus, so the Status value gets clobbered before it gets stored. This will eventually result in the Status register getting a TCStatus value, which has some bits on common, but isn't identical and sooner or later Bad Things will happen. I'm a little surprised this wasn't caught by visual inspection of the patch. Possible solutions would include reverting the store of the CP0_STATUS value to the block above the #ifdef, or, to retain whatever performance advantage was obtained by moving the store downward, to use v0/$2 instead of v1/$3, as the staging register for the TCStatus value. I'd lean toward the second option, but I'm not in a position to test and submit a patch just now. Regards, Kevin K. On 12/23/10 1:09 PM, STUART VENTERS wrote: > Kevin, > > I'm not sure if it's useful, > but finally I got the time to look at the two kernel versions Anoop pointed out. > works 2.6.32-stable with patch 804 > works_not 2.6.33-stable > > greping for files with CONFIG_MIPS_MT_SMTC > and looking for timer interrupt related stuff found the following differences: > > > arch/mips/include/asm/irq.h > arch/mips/kernel/irq.c > do_IRQ > > arch/mips/include/asm/stackframe.h > SAVE_SOME SAVE_TEMP get/set_saved_sp > > arch/mips/include/asm/time.h > clocksource_set_clock > > arch/mips/kernel/process.c > cpu_idle > > arch/mips/kernel/smtc.c > __irq_entry > ipi_decode > SMTC_CLOCK_TICK > > > Enclosed are the two subsets of files for a more expert look. > > I'll try to look in more detail after Christmas. > > > Cheers, > > Stuart > > > >