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=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 489FCC47082 for ; Mon, 31 May 2021 13:46:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2DE0461A46 for ; Mon, 31 May 2021 13:46:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232740AbhEaNs3 (ORCPT ); Mon, 31 May 2021 09:48:29 -0400 Received: from mga09.intel.com ([134.134.136.24]:64675 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232211AbhEaNq1 (ORCPT ); Mon, 31 May 2021 09:46:27 -0400 IronPort-SDR: rWIiFXlmH4zdN3MQHcGuH9XDSdfOgk73Sjb4KfLor2/0vDNIiNEf5VZ8+rjl7jpxS4SrdZ9IZA NAyH1zFDHpPA== X-IronPort-AV: E=McAfee;i="6200,9189,10000"; a="203364532" X-IronPort-AV: E=Sophos;i="5.83,237,1616482800"; d="scan'208";a="203364532" Received: from orsmga005.jf.intel.com ([10.7.209.41]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 31 May 2021 06:34:15 -0700 IronPort-SDR: uur1sQVNisXsHxx4ZLLEnPKTrgJXKdL2G2SyRHCCUtZDYUL8ROPLb+j5XnVHubbratyEjtJWHK o4jVMcFUPSug== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.83,237,1616482800"; d="scan'208";a="616538368" Received: from black.fi.intel.com ([10.237.72.28]) by orsmga005.jf.intel.com with ESMTP; 31 May 2021 06:34:13 -0700 Received: by black.fi.intel.com (Postfix, from userid 1001) id 0CEF312A; Mon, 31 May 2021 16:34:35 +0300 (EEST) From: Mika Westerberg To: Bjorn Helgaas , "Rafael J. Wysocki" Cc: Utkarsh H Patel , Koba Ko , Rajat Jain , Kai-Heng Feng , Mika Westerberg , linux-pci@vger.kernel.org Subject: [PATCH v2] PCI/PM: Target PM state is D3cold if the upstream bridge is power manageable Date: Mon, 31 May 2021 16:34:35 +0300 Message-Id: <20210531133435.53259-1-mika.westerberg@linux.intel.com> X-Mailer: git-send-email 2.30.2 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org Some PCIe devices only support PME (Power Management Event) from D3cold. One example is ASMedia xHCI controller: 11:00.0 USB controller: ASMedia Technology Inc. ASM1042A USB 3.0 Host Controller (prog-if 30 [XHCI]) ... Capabilities: [78] Power Management version 3 Flags: PMEClk- DSI- D1- D2- AuxCurrent=55mA PME(D0-,D1-,D2-,D3hot-,D3cold+) Status: D0 NoSoftRst+ PME-Enable- DSel=0 DScale=0 PME- With such devices, if it has wake enabled, the kernel selects lowest possible power state to be D0 in pci_target_state(). This is problematic because it prevents the root port it is connected to enter low power state too which makes the system consume more energy than necessary. The problem in pci_target_state() is that it only accounts the "current" device state, so when the bridge above it (a root port for instance) is transitioned into D3hot the device transitions into D3cold. This is because when the root port is first transitioned into D3hot then the ACPI power resource is turned off which puts the PCIe link to L2/L3 (and the root port and the device are in D3cold). If the root port is kept in D3hot it still means that the device below it is still effectively in D3cold as no configuration messages pass through. Furthermore the implementation note of PCIe 5.0 sec 5.3.1.4 says that the device should expect to be transitioned into D3cold soon after its link transitions into L2/L3 Ready state. Taking the above into consideration, instead of forcing the device stay in D0 we look at the upstream bridge and whether it is allowed to enter D3 (hot/cold). If this is the case we conclude that the actual target state of the device is D3cold. This also follows the logic in pci_set_power_state() that sets power state of the subordinate devices to D3cold after the bridge itself is transitioned into D3cold. Reported-by: Utkarsh H Patel Reported-by: Koba Ko Tested-by: Koba Ko Acked-by: Kai-Heng Feng Signed-off-by: Mika Westerberg --- Previous version of the patch can be found here: https://patchwork.kernel.org/project/linux-pci/patch/20210510102647.40322-1-mika.westerberg@linux.intel.com/ Changes from the previous version: * Added Ack from Kai-Heng * Reworked the commit log according to Bjorn's comments (I tried my best to answer the questions and explain the issue). * Expanded the comment to mention why the target state is D3cold. drivers/pci/pci.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index b717680377a9..71c6a6437406 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -2578,8 +2578,21 @@ static pci_power_t pci_target_state(struct pci_dev *dev, bool wakeup) return target_state; } - if (!dev->pm_cap) + if (!dev->pm_cap) { target_state = PCI_D0; + } else { + struct pci_dev *bridge; + + /* + * Look at the upstream bridge and whether it is allowed to + * enter D3hot (or D3cold). In both cases this device is + * not accessible anymore and its effective power state + * becomes D3cold. + */ + bridge = pci_upstream_bridge(dev); + if (bridge && pci_bridge_d3_possible(bridge)) + target_state = PCI_D3cold; + } /* * If the device is in D3cold even though it's not power-manageable by -- 2.30.2