From owner-freebsd-arch@FreeBSD.ORG Fri Dec 6 05:44:04 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 ACDEF2BA for ; Fri, 6 Dec 2013 05:44:04 +0000 (UTC) Received: from mail-ie0-f172.google.com (mail-ie0-f172.google.com [209.85.223.172]) (using TLSv1 with cipher ECDHE-RSA-RC4-SHA (128/128 bits)) (No client certificate requested) by mx1.freebsd.org (Postfix) with ESMTPS id 75EAC1E05 for ; Fri, 6 Dec 2013 05:44:04 +0000 (UTC) Received: by mail-ie0-f172.google.com with SMTP id qd12so444617ieb.31 for ; Thu, 05 Dec 2013 21:43:58 -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=jwp/fDvfvD+GkvEUR6w6sMKiz6ADYpkmusPoVmKtAXQ=; b=b1WjEhivawkJkxXZcNWrUKw7FURuc+ls0f/SOJJmvWUAJ2NsQq4kDXKYA+4PqyOtvw EcdXWCkKyYaP6ZBdbDwx3E4pjaMIPHr2fef0pJdCA7z8wkamGDYAP5RcXdHpIfVj9l0o kTI+VcOWltB+pKtgyiH2v4kDV0Ys6KYaxVj8u+tvwQVOayhY7ZuRpuI8iGeB8nM1dT3a UxhJuvMi36dwfIPgIlgcFkOUq3LMHRoVyvPnE7yYsZJklh6HwpM7BkXzzNVfE0bp3t3v W6re1UPRCOlxtQPP+mmZHpVAmN6zdys1Wd31FNdWDZMvNgwE7Ix662t4pth6VxDQbTli HTtA== X-Gm-Message-State: ALoCoQm9sDPGI1JsIGhnnXmsSoaSzGCD47BSMo+6lbMmd27ysCje8STn00aTzMZDL1hCVWd/2D/f X-Received: by 10.50.30.166 with SMTP id t6mr901474igh.7.1386308637959; Thu, 05 Dec 2013 21:43:57 -0800 (PST) Received: from fusion-mac.bsdimp.com (50-78-194-198-static.hfc.comcastbusiness.net. [50.78.194.198]) by mx.google.com with ESMTPSA id qi3sm2028635igc.8.2013.12.05.21.43.57 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Thu, 05 Dec 2013 21:43:57 -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: Date: Thu, 5 Dec 2013 22:43:56 -0700 Content-Transfer-Encoding: quoted-printable Message-Id: References: To: Eitan Adler X-Mailer: Apple Mail (2.1085) Cc: "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 05:44:04 -0000 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? 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. Warner