From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.7 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 29B23C43387 for ; Tue, 18 Dec 2018 20:58:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B51D6218B0 for ; Tue, 18 Dec 2018 20:58:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1545166738; bh=ZkHBouKwD9dlWFsZDfNhZAD+PkjfmWVyJxr/vmD4o/o=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=IsahSIbkY98E++JA3W5bLEiA7lBFjpyWKZA7PmRrJH4HBVi2ZoHg0MkmnG/trQA75 TcaIqSmCp+/rjWSQtKaSOIhhZ4JWG5VtMhTk2U84bZMeP6WwnmCW0oWrcCoG3KxzBe j9UU8qqIAPlfwPkjBRDFfbNq8KSKtwl94yP8ZnxI= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726451AbeLRU65 (ORCPT ); Tue, 18 Dec 2018 15:58:57 -0500 Received: from mail.kernel.org ([198.145.29.99]:47142 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726422AbeLRU65 (ORCPT ); Tue, 18 Dec 2018 15:58:57 -0500 Received: from localhost (unknown [69.71.4.100]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 5A560217D9; Tue, 18 Dec 2018 20:58:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1545166736; bh=ZkHBouKwD9dlWFsZDfNhZAD+PkjfmWVyJxr/vmD4o/o=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=TKd31GC7rH5MlmPAJsA+U8Ca5fFkEuSkqYnM4XjJIjmoH3KDcAqiW9HEHBlt1m4T6 sHbTwcg2DQQAzdUEmC/5cdNCAfBVyQlo0vM7clUzczXXxzWqrVLlk6Ocoz8GwPj4bQ kHyFgC4e27OZiee0Ul7JzBwP9JVifZRD9XhRR04c= Date: Tue, 18 Dec 2018 14:58:50 -0600 From: Bjorn Helgaas To: Mika Westerberg Cc: "Rafael J. Wysocki" , Kedar A Dongre , Lukas Wunner , linux-pci@vger.kernel.org, linux-acpi@vger.kernel.org Subject: Re: [PATCH] PCI: Blacklist power management of Gigabyte X299 DESIGNARE EX PCIe ports Message-ID: <20181218205850.GA12763@google.com> References: <20181204112048.35378-1-mika.westerberg@linux.intel.com> <20181217202827.GC28981@google.com> <20181218085518.GI2469@lahna.fi.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181218085518.GI2469@lahna.fi.intel.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Tue, Dec 18, 2018 at 10:55:18AM +0200, Mika Westerberg wrote: > On Mon, Dec 17, 2018 at 02:28:27PM -0600, Bjorn Helgaas wrote: > > On Tue, Dec 04, 2018 at 02:20:48PM +0300, Mika Westerberg wrote: > > > Gigabyte X299 DESIGNARE EX motherboard has one PCIe root port that is > > > connected to an Alpine Ridge Thunderbolt controller. This port has slot > > > implemented bit set in the config space but other than that it is not > > > hotplug capable in the sense we are expecting in Linux (it has > > > dev->is_hotplug_bridge set to 0): > > > > > > 00:1c.4 PCI bridge: Intel Corporation 200 Series PCH PCI Express Root Port #5 > > > Bus: primary=00, secondary=05, subordinate=46, sec-latency=0 > > > Memory behind bridge: 78000000-8fffffff [size=384M] > > > Prefetchable memory behind bridge: 00003800f8000000-00003800ffffffff [size=128M] > > > ... > > > Capabilities: [40] Express (v2) Root Port (Slot+), MSI 00 > > > ... > > > SltCap: AttnBtn- PwrCtrl- MRL- AttnInd- PwrInd- HotPlug- Surprise- > > > Slot #8, PowerLimit 25.000W; Interlock- NoCompl+ > > > SltCtl: Enable: AttnBtn- PwrFlt- MRL- PresDet- CmdCplt- HPIrq- LinkChg- > > > Control: AttnInd Unknown, PwrInd Unknown, Power- Interlock- > > > SltSta: Status: AttnBtn- PowerFlt- MRL- CmdCplt- PresDet- Interlock- > > > Changed: MRL- PresDet+ LinkState+ > > > > > > This system is using ACPI based hotplug to notify the OS that it needs > > > to rescan the PCI bus (ACPI hotplug). > > > > > > If there is nothing connected in any of the Thunderbolt ports the root > > > port will not have any runtime PM active children and is thus > > > automatically runtime suspended pretty soon after boot by PCI PM core. > > > Now, when a device is connected the BIOS SMI handler responsible for > > > enumerating newly added devices is not able to find anything because the > > > port is in D3. > > > > Ugh. I don't see how this is a maintainable solution. Are we going > > to have to just update this blacklist empirically as we get reports of > > systems that are "broken"? > > I was hoping not but for that we would need to have some means to > identify these. What you suggest below might be one way to avoid adding > the blacklist. > > > I say "broken" because I don't think we can point to anything here > > that doesn't conform to the specs, so maybe we tripped over something > > that *should* be covered in the spec, or maybe we're just not > > interpreting something correctly. > > That is indeed possible. > > > For example, it looks like PCI_EXP_FLAGS_SLOT is set, but Linux > > basically ignores it. Maybe if PCI_EXP_FLAGS_SLOT is set but we > > aren't using pciehp, we should assume any hotplug would be handled via > > acpiphp? And in that case, we should avoid doing anything that would > > prevent platform firmware from enumerating things below the bridge? > > I don't see why that would not work. This could cause "power regression" > on some systems but I think that's better than systems that do not work > at all. Yeah, I think that would be better, assuming it wouldn't cause a flood of power regressions. I'd even rather have a whitelist of systems where we use acpiphp and it's safe to do power management. > > Is there a bugzilla or any other URL we could include here to help with > > future changes in this area? > > No, this was reported internally. > > I can file one if you think it is helpful. I think a kernel.org bugzilla that archived the "lspci -vv", a dmesg log, and an acpidump might be helpful. Bjorn