From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from na01-bl2-obe.outbound.protection.outlook.com (mail-bl2on0117.outbound.protection.outlook.com [65.55.169.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 665C11A0490 for ; Thu, 11 Dec 2014 10:50:51 +1100 (AEDT) Message-ID: <1418255437.5581.45.camel@freescale.com> Subject: Re: [PATCH 2 1/4] powerpc: drop the ability to tweak SMT mode at boot time From: Scott Wood To: Michael Ellerman Date: Wed, 10 Dec 2014 17:50:37 -0600 In-Reply-To: <1418177689.30244.4.camel@concordia> References: <20141205150405.11028.27445.stgit@bahia.lab.toulouse-stg.fr.ibm.com> <20141205151341.11028.47570.stgit@bahia.lab.toulouse-stg.fr.ibm.com> <1417805565.334.15.camel@freescale.com> <1418098262.527.1.camel@concordia> <1418159084.5581.32.camel@freescale.com> <1418169405.30244.1.camel@concordia> <1418170485.5581.39.camel@freescale.com> <1418177689.30244.4.camel@concordia> Content-Type: text/plain; charset="UTF-8" MIME-Version: 1.0 Cc: linuxppc-dev@lists.ozlabs.org, Greg Kurz List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Wed, 2014-12-10 at 13:14 +1100, Michael Ellerman wrote: > On Tue, 2014-12-09 at 18:14 -0600, Scott Wood wrote: > > What benefit is there to ignoring "scripture" here? Going from an easy > > to use command line option to needing to mess around with the dts file > > is not a usability improvement. If you want to make it Freescale-only, > > fine. If you want to push me to fix the problems with the > > implementation, fine. > > It's easy to use but it doesn't necessarily work. > > You said in your other mail to Greg "Sometimes it's useful to ensure that the > second thread has never run when debugging a problem.". > > But you don't know that, for all you know your firmware has started the thread > and it's busy looping somewhere. Perhaps you guys know that your firmware > doesn't do that, but it's still a hack. I know that our firmware doesn't do that, and I can verify by reading the relevant register. > We end up with cpus in the present map, but we have no idea where they are or > what they are doing. Can we check smt-enabled a little earlier and refrain from marking the secondary threads as present if smt is disabled? > So as far as I'm concerned it's only useful as a debugging hack, and one that > we don't really use anymore. But if you guys think it's useful then we'll keep > it. > > I'll work out with Greg what the cleanest solution is. > > It looks like you only need it on e6500? Which is platforms/85xx I think. > Anywhere else? Yes, just e6500. -Scott