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=-10.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 84B7FC433E2 for ; Thu, 10 Sep 2020 19:19:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 37E5921D81 for ; Thu, 10 Sep 2020 19:19:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1599765568; bh=mCK9lYBNZqSn4KSAm3WuF8IQaNvd1jqOlTKFBZbL4L0=; h=Date:From:To:Cc:Subject:In-Reply-To:List-ID:From; b=zuhDUF5wv3GfKT01JdQ0nyj12qBPMC3fBWviaYMOx5twHhoZjGG3MdVc4E0Qdz93w eFauBzmhs8fPHRBvD98pezekmCJsoMAIqbwdgU5sQtW8FsBjGX9SJgngn9Ef88wa10 lWaYlSfOD31sTsm/ViwKo0v3shTY9Evgk0+7aLkY= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726293AbgIJTSe (ORCPT ); Thu, 10 Sep 2020 15:18:34 -0400 Received: from mail.kernel.org ([198.145.29.99]:43904 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726789AbgIJTRv (ORCPT ); Thu, 10 Sep 2020 15:17:51 -0400 Received: from localhost (52.sub-72-107-123.myvzw.com [72.107.123.52]) (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 BE877214F1; Thu, 10 Sep 2020 19:17:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1599765462; bh=mCK9lYBNZqSn4KSAm3WuF8IQaNvd1jqOlTKFBZbL4L0=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=vFg3UGl7sW9LPijHXHUL4vz/4VrdD8lFwQsBPEeUE0rb65k+7taHWFdym6lxxLku7 qWkjO15KlkV/G1nqxCsr+cKt1OePexPt9Ckf8T9wQzj/lmXkHr+5guqRxIWC9kJBqu o/b3mBtIka+bHp7l6yTgntYDI0Ytwq012pTiTFIo= Date: Thu, 10 Sep 2020 14:17:40 -0500 From: Bjorn Helgaas To: "Derrick, Jonathan" Cc: "wangxiongfeng2@huawei.com" , "kw@linux.com" , "hkallweit1@gmail.com" , "kai.heng.feng@canonical.com" , "refactormyself@gmail.com" , "linux-kernel@vger.kernel.org" , "mika.westerberg@linux.intel.com" , "Mario.Limonciello@dell.com" , "linux-pci@vger.kernel.org" , "bhelgaas@google.com" , "Wysocki, Rafael J" Subject: Re: [PATCH] PCI/ASPM: Enable ASPM for links under VMD domain Message-ID: <20200910191740.GA806068@bjorn-Precision-5520> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <0f902d555deb423ef1c79835b23c917be2633162.camel@intel.com> Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Thu, Sep 10, 2020 at 06:52:48PM +0000, Derrick, Jonathan wrote: > On Thu, 2020-09-10 at 12:38 -0500, Bjorn Helgaas wrote: > > On Thu, Sep 10, 2020 at 04:33:39PM +0000, Derrick, Jonathan wrote: > > > On Wed, 2020-09-09 at 20:55 -0500, Bjorn Helgaas wrote: > > > > On Fri, Aug 21, 2020 at 08:32:20PM +0800, Kai-Heng Feng wrote: > > > > > New Intel laptops with VMD cannot reach deeper power saving state, > > > > > renders very short battery time. > > > > > > > > > > As BIOS may not be able to program the config space for devices under > > > > > VMD domain, ASPM needs to be programmed manually by software. This is > > > > > also the case under Windows. > > > > > > > > > > The VMD controller itself is a root complex integrated endpoint that > > > > > doesn't have ASPM capability, so we can't propagate the ASPM settings to > > > > > devices under it. Hence, simply apply ASPM_STATE_ALL to the links under > > > > > VMD domain, unsupported states will be cleared out anyway. > > > > > > > > > > Signed-off-by: Kai-Heng Feng > > > > > --- > > > > > drivers/pci/pcie/aspm.c | 3 ++- > > > > > drivers/pci/quirks.c | 11 +++++++++++ > > > > > include/linux/pci.h | 2 ++ > > > > > 3 files changed, 15 insertions(+), 1 deletion(-) > > > > > > > > > > diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c > > > > > index 253c30cc1967..dcc002dbca19 100644 > > > > > --- a/drivers/pci/pcie/aspm.c > > > > > +++ b/drivers/pci/pcie/aspm.c > > > > > @@ -624,7 +624,8 @@ static void pcie_aspm_cap_init(struct pcie_link_state *link, int blacklist) > > > > > aspm_calc_l1ss_info(link, &upreg, &dwreg); > > > > > > > > > > /* Save default state */ > > > > > - link->aspm_default = link->aspm_enabled; > > > > > + link->aspm_default = parent->dev_flags & PCI_DEV_FLAGS_ENABLE_ASPM ? > > > > > + ASPM_STATE_ALL : link->aspm_enabled; > > > > > > > > This function is ridiculously complicated already, and I really don't > > > > want to make it worse. > > > > > > > > What exactly is the PCIe topology here? Apparently the VMD controller > > > > is a Root Complex Integrated Endpoint, so it's a Type 0 (non-bridge) > > > > device. And it has no Link, hence no Link Capabilities or Control and > > > > hence no ASPM-related bits. Right? > > > > > > That's correct. VMD is the Type 0 device providing config/mmio > > > apertures to another segment and MSI/X remapping. No link and no ASPM > > > related bits. > > > > > > Hierarchy is usually something like: > > > > > > Segment 0 | VMD segment > > > Root Complex -> VMD | Type 0 (RP/Bridge; physical slot) - Type 1 > > > | Type 0 (RP/Bridge; physical slot) - Type 1 > > > > > > > And the devices under the VMD controller? I guess they are regular > > > > PCIe Endpoints, Switch Ports, etc? Obviously there's a Link involved > > > > somewhere. Does the VMD controller have some magic, non-architected > > > > Port on the downstream side? > > > > > > Correct: Type 0 and Type 1 devices, and any number of Switch ports as > > > it's usually pinned out to physical slot. > > > > > > > Does this patch enable ASPM on this magic Link between VMD and the > > > > next device? Configuring ASPM correctly requires knowledge and knobs > > > > from both ends of the Link, and apparently we don't have those for the > > > > VMD end. > > > > > > VMD itself doesn't have the link to it's domain. It's really just the > > > config/mmio aperture and MSI/X remapper. The PCIe link is between the > > > Type 0 and Type 1 devices on the VMD domain. So fortunately the VMD > > > itself is not the upstream part of the link. > > > > > > > Or is it for Links deeper in the hierarchy? I assume those should > > > > just work already, although there might be issues with latency > > > > computation, etc., because we may not be able to account for the part > > > > of the path above VMD. > > > > > > That's correct. This is for the links within the domain itself, such as > > > between a type 0 and NVMe device. > > > > OK, great. So IIUC, below the VMD, there is a Root Port, and the Root > > Port has a link to some Endpoint or Switch, e.g., an NVMe device. And > > we just want to enable ASPM on that link. > > > > That should not be a special case; we should be able to make this so > > it Just Works. Based on this patch, I guess the reason it doesn't > > work is because link->aspm_enabled for that link isn't set correctly. > > > > So is this just a consequence of us depending on the initial Link > > Control value from BIOS? That seems like something we shouldn't > > really depend on. > > > That's the crux. There's always pcie_aspm=force. > Something I've wondered is if there is a way we could 'discover' if the > link is ASPM safe? Sure. Link Capabilities is supposed to tell us that. If aspm.c depends on the BIOS settings, I think that's a design mistake. But what CONFIG_PCIEASPM_* setting are you using? The default is CONFIG_PCIEASPM_DEFAULT, which literally means "Use the BIOS defaults". If you're using that, and BIOS doesn't enable ASPM below VMD, I guess aspm.c will leave it disabled, and that seems like it would be the expected behavior. Does "pcie_aspm=force" really help you? I don't see any uses of it that should apply to your situation. Bjorn