From owner-freebsd-arch@FreeBSD.ORG Fri Dec 6 20:52:16 2013 Return-Path: Delivered-To: arch@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id EB902B41 for ; Fri, 6 Dec 2013 20:52:15 +0000 (UTC) Received: from mail-ie0-f176.google.com (mail-ie0-f176.google.com [209.85.223.176]) (using TLSv1 with cipher ECDHE-RSA-RC4-SHA (128/128 bits)) (No client certificate requested) by mx1.freebsd.org (Postfix) with ESMTPS id B3CAE1FE7 for ; Fri, 6 Dec 2013 20:52:15 +0000 (UTC) Received: by mail-ie0-f176.google.com with SMTP id at1so2181449iec.7 for ; Fri, 06 Dec 2013 12:52:08 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:sender:subject:mime-version:content-type:from :in-reply-to:date:cc:content-transfer-encoding:message-id:references :to; bh=VL8+KTU/oVzRbyNgXyKs4U2b2FqLQRgzIWf3RriDLCI=; b=SJV4u0BBBoW/ikjPMnr82mdXuTLtRJh/pVcH/LlDLYKVmAKKMBzLmGSKcWsIv+HPgA oOU1Wqlany3re2i1SZymz3R03C/25Wu3aMX8eoIBkFjQFBohKSqDfRxGR5wpg6/T0ddk oO43lIYu/I06+YcrxuxxoUpZDfTTKOdFvRvqMNVVlzQ/vfL52k1CjCiBag6WGiRG+7MM 7e4tjhoM8SA7WiLR9lOCqX2CdO7yNJxwVF0Htitg+CeGPjwWT6jdibWOSM2GeW/U7j3y Ec1NY1WHPto79kTgV4/J65XE0YVxaHZeZkwLXvYmRJb5v1JRyuDeHcmx38yINYF10xJR 3/ow== X-Gm-Message-State: ALoCoQn2ic1w/FbOQfAbdL3HTVryJZpU/Xk136j2IgcaxDIMETx19dPdtCpLmOeBy+GmK9BIRzOB X-Received: by 10.50.1.102 with SMTP id 6mr4665907igl.0.1386363128496; Fri, 06 Dec 2013 12:52:08 -0800 (PST) Received: from monkey-bot.int.fusionio.com ([209.117.142.2]) by mx.google.com with ESMTPSA id o1sm5526729igh.9.2013.12.06.12.52.07 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Fri, 06 Dec 2013 12:52:07 -0800 (PST) Sender: Warner Losh Subject: Re: hw.pci.do_power_nodriver=3 Mime-Version: 1.0 (Apple Message framework v1085) Content-Type: text/plain; charset=us-ascii From: Warner Losh In-Reply-To: <20131206202616.GH55638@funkthat.com> Date: Fri, 6 Dec 2013 13:52:06 -0700 Content-Transfer-Encoding: quoted-printable Message-Id: <91CBC153-C832-4350-8E19-24783A1CFA63@bsdimp.com> References: <20131206202616.GH55638@funkthat.com> To: John-Mark Gurney X-Mailer: Apple Mail (2.1085) 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 20:52:16 -0000 On Dec 6, 2013, at 1:26 PM, John-Mark Gurney wrote: > Warner Losh wrote this message on Thu, Dec 05, 2013 at 22:43 -0700: >>=20 >> On Dec 5, 2013, at 9:12 PM, Eitan Adler wrote: >>> Is there any reason we can not set hw.pci.do_power_nodriver=3D3 by = default? >>>=20 >>> 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? >>=20 >> The reason it was for Adaptec RAID controllers. >>=20 >> They had a weird topology: >>=20 >> <-------------------- aac based card = --------------------------> >> pci bus ---- pci bridge ---- pci bus ---+----- some chip with = driver >> = +----- chip without driver >>=20 >> 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. >>=20 >> 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. >=20 > 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... >=20 > Then maybe after a few years, maybe not 11, but for 12, we can keep it > on by default for a release? Scott and I talked about a possible solution that would be safe. Once I = have that implemented, we can likely switch things over... Warner