From owner-freebsd-arch@FreeBSD.ORG Fri Dec 6 20:26:21 2013 Return-Path: Delivered-To: arch@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 5B532BCC for ; Fri, 6 Dec 2013 20:26:21 +0000 (UTC) Received: from h2.funkthat.com (gate2.funkthat.com [208.87.223.18]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.freebsd.org (Postfix) with ESMTPS id 19CAF1DDF for ; Fri, 6 Dec 2013 20:26:20 +0000 (UTC) Received: from h2.funkthat.com (localhost [127.0.0.1]) by h2.funkthat.com (8.14.3/8.14.3) with ESMTP id rB6KQHDC092412 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Fri, 6 Dec 2013 12:26:17 -0800 (PST) (envelope-from jmg@h2.funkthat.com) Received: (from jmg@localhost) by h2.funkthat.com (8.14.3/8.14.3/Submit) id rB6KQGPu092411; Fri, 6 Dec 2013 12:26:16 -0800 (PST) (envelope-from jmg) Date: Fri, 6 Dec 2013 12:26:16 -0800 From: John-Mark Gurney To: Warner Losh Subject: Re: hw.pci.do_power_nodriver=3 Message-ID: <20131206202616.GH55638@funkthat.com> Mail-Followup-To: Warner Losh , Eitan Adler , "freebsd-arch@freebsd.org" References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.3i X-Operating-System: FreeBSD 7.2-RELEASE i386 X-PGP-Fingerprint: 54BA 873B 6515 3F10 9E88 9322 9CB1 8F74 6D3F A396 X-Files: The truth is out there X-URL: http://resnet.uoregon.edu/~gurney_j/ X-Resume: http://resnet.uoregon.edu/~gurney_j/resume.html X-to-the-FBI-CIA-and-NSA: HI! HOW YA DOIN? can i haz chizburger? X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.2 (h2.funkthat.com [127.0.0.1]); Fri, 06 Dec 2013 12:26:17 -0800 (PST) Cc: Eitan Adler , "freebsd-arch@freebsd.org" X-BeenThere: freebsd-arch@freebsd.org X-Mailman-Version: 2.1.17 Precedence: list List-Id: Discussion related to FreeBSD architecture List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 06 Dec 2013 20:26:21 -0000 Warner Losh wrote this message on Thu, Dec 05, 2013 at 22:43 -0700: > > On Dec 5, 2013, at 9:12 PM, Eitan Adler wrote: > > Is there any reason we can not set hw.pci.do_power_nodriver=3 by default? > > > > My understanding is that there were problems with hardware being > > powered off and not being powered back on when drivers were loaded. > > Is this still a concern? If yes, can we flip the switch in HEAD and > > fix the drivers? > > The reason it was for Adaptec RAID controllers. > > They had a weird topology: > > <-------------------- aac based card --------------------------> > pci bus ---- pci bridge ---- pci bus ---+----- some chip with driver > +----- chip without driver > > so, when the enumeration code saw that there was no driver attached to the second chip, it would power it down. Turns out, this chip, while it didn't have a driver, was critical to the proper functioning of the RAID card. Scott Long turned off the default power saving because he was worried there were other parts like this. In addition, in an abundance of caution, he also created stub drivers for the second chip for each of the then known aac cards. > > Since then, it is unknown if others have followed this design or not, so it is unknown our exposure if we were to flip this to have a different default. Should we flip this on by default in HEAD to help expose these issues? It is expected that people running HEAD spend a little time helping us debug issues, and if they don't want to take the risk, they can change the default... Then maybe after a few years, maybe not 11, but for 12, we can keep it on by default for a release? -- John-Mark Gurney Voice: +1 415 225 5579 "All that I will do, has been done, All that I have, has not."