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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 34DDAC001B0 for ; Wed, 5 Jul 2023 20:06:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233438AbjGEUGX (ORCPT ); Wed, 5 Jul 2023 16:06:23 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35536 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232618AbjGEUGU (ORCPT ); Wed, 5 Jul 2023 16:06:20 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1FD11188; Wed, 5 Jul 2023 13:06:20 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id A8141616FB; Wed, 5 Jul 2023 20:06:19 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id BA81FC433C7; Wed, 5 Jul 2023 20:06:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1688587579; bh=z5pOaz2o7vAP2YYNhfS0EUOnW70/UEHkLQ7tR3WqAaY=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=TJPC1G02VrF+X/MQY3zvnWf6w99sv8SGZs9esbh15UwTqy6jsR65e63GQtj722Ga+ sq/DUutey0colk4gWe6ebEUHNlsAzuvaAMfhFi48dzCaiPsgGA1nBM9bqPRdSOvBWQ 2wuAP8qRvEJSBlQknfZWecUcsfm6SmBXo9yISo4Ce991HvVCsB9Gvojx/CkIoqYIPo dU9ELI48fKtEvId/VkyrFa4H/lvR2vO14QoutBBvhAN2as+ABkqX4wALhxwK/Vi2Ag y+QEdaIyU1c8hHh20mDzai1AswiWVRQy6XL3s+kRSwzExHpWC6f/jhrRDU4sc8QqWj jnfdHKJhlNhFg== Date: Wed, 5 Jul 2023 15:06:17 -0500 From: Bjorn Helgaas To: Kai-Heng Feng Cc: Kuppuswamy Sathyanarayanan , linux-pci@vger.kernel.org, "Rafael J. Wysocki" , linux-kernel@vger.kernel.org, Vidya Sagar , Michael Bottini , "Limonciello, Mario" , intel-wired-lan@osuosl.org, bhelgaas@google.com, Mika Westerberg Subject: Re: [Intel-wired-lan] [PATCH] PCI/ASPM: Enable ASPM on external PCIe devices Message-ID: <20230705200617.GA72825@bhelgaas> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jun 28, 2023 at 01:09:49PM +0800, Kai-Heng Feng wrote: > On Wed, Jun 28, 2023 at 4:54 AM Bjorn Helgaas wrote: > > On Tue, Jun 27, 2023 at 04:35:25PM +0800, Kai-Heng Feng wrote: > > > On Fri, Jun 23, 2023 at 7:06 AM Bjorn Helgaas wrote: > > > > On Tue, Jun 20, 2023 at 01:36:59PM -0500, Limonciello, Mario wrote: > > It's perfectly fine for the IP to support PCI features that are not > > and can not be enabled in a system design. But I expect that > > strapping or firmware would disable those features so they are not > > advertised in config space. > > > > If BIOS leaves features disabled because they cannot work, but at the > > same time leaves them advertised in config space, I'd say that's a > > BIOS defect. In that case, we should have a DMI quirk or something to > > work around the defect. > > That means most if not all BIOS are defected. > BIOS vendors and ODM never bothered (and probably will not) to change > the capabilities advertised by config space because "it already works > under Windows". This is what seems strange to me. Are you saying that Windows never enables these power-saving features? Or that Windows includes quirks for all these broken BIOSes? Neither idea seems very convincing. > > > So the logic is to ignore the capability and trust the default set > > > by BIOS. > > > > I think limiting ASPM support to whatever BIOS configured at boot-time > > is problematic. I don't think we can assume that all platforms have > > firmware that configures ASPM as aggressively as possible, and > > obviously firmware won't configure hot-added devices at all (in > > general; I know ACPI _HPX can do some of that). > > Totally agree. I was not suggesting to limiting the setting at all. > A boot-time parameter to flip ASPM setting is very useful. If none has > been set, default to BIOS setting. A boot-time parameter for debugging and workarounds is fine. IMO, needing a boot-time parameter in the course of normal operation is not OK. Bjorn