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=-14.0 required=3.0 tests=BAYES_00,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,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 C06AFC433E1 for ; Wed, 24 Mar 2021 15:44:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 99001619FF for ; Wed, 24 Mar 2021 15:44:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236751AbhCXPn5 (ORCPT ); Wed, 24 Mar 2021 11:43:57 -0400 Received: from mail-ot1-f53.google.com ([209.85.210.53]:40489 "EHLO mail-ot1-f53.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236704AbhCXPn0 (ORCPT ); Wed, 24 Mar 2021 11:43:26 -0400 Received: by mail-ot1-f53.google.com with SMTP id w31-20020a9d36220000b02901f2cbfc9743so23147728otb.7; Wed, 24 Mar 2021 08:43:26 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=2LlnlKXH3YzdwPwZvOCp+nvzSAq22UqWfFbrRfMlBJc=; b=eZ9uKHrR5WrnJOBBzqa1m1UU/gUVA9ls3rbI7C3VL1xRgTAShPfML7QdfufX38OBFC IkZqA4ZTD6pRnDfgoxFR8XtGy1hKfmB7pQ2oBFvRxYlInoV3gOCOCovZn1aPJbRO7gI/ 3KK6KSd3I7Qp7BCbhlydgzyj7EgIC6AlLi8epvb+x8StkUsnKX43dVG9EBuhJIESuM/Z uNrAGUfG6dQO7u0dsKOs6lok+OXd81kWm8N5YjvowrIiiWYmzsiQLtJFMTZBKLSnATkl pdcjHmXU61CVF2TVJQ5n0fvfeu9YrEIpVx7diKR4ODLKIJ/hphCogmvuvDOyO/+ONI1q /IBw== X-Gm-Message-State: AOAM5328Ee+d0cOEt7JMSGU5uOpOIy4iSb4wcexX/ccZ0sH9ehDknwmk lxa6ODqilxB7vkJgJxg52PII1JE1AvosJr1ZjNI= X-Google-Smtp-Source: ABdhPJxNMKZPyOtlHWS9CFGr1m+5WKdkr7FCUdWw3lktEmn/S/Ih+XgaUBMc39h6BnJOQ1THP81t3kXd4HWkbwC8oLk= X-Received: by 2002:a05:6830:20d2:: with SMTP id z18mr3673941otq.260.1616600605781; Wed, 24 Mar 2021 08:43:25 -0700 (PDT) MIME-Version: 1.0 References: <3219454.74lMxhSOWB@kreacher> In-Reply-To: From: "Rafael J. Wysocki" Date: Wed, 24 Mar 2021 16:43:14 +0100 Message-ID: Subject: Re: [PATCH] PCI: PM: Do not read power state in pci_enable_device_flags() To: "Rafael J. Wysocki" Cc: Bjorn Helgaas , Maximilian Luz , LKML , Linux PCI , Linux PM , Mika Westerberg , Linux ACPI Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Mon, Mar 22, 2021 at 3:32 PM Rafael J. Wysocki wrote: > > On Tue, Mar 16, 2021 at 4:52 PM Rafael J. Wysocki wrote: > > > > From: Rafael J. Wysocki > > > > It should not be necessary to update the current_state field of > > struct pci_dev in pci_enable_device_flags() before calling > > do_pci_enable_device() for the device, because none of the > > code between that point and the pci_set_power_state() call in > > do_pci_enable_device() invoked later depends on it. > > > > Moreover, doing that is actively harmful in some cases. For example, > > if the given PCI device depends on an ACPI power resource whose _STA > > method initially returns 0 ("off"), but the config space of the PCI > > device is accessible and the power state retrieved from the > > PCI_PM_CTRL register is D0, the current_state field in the struct > > pci_dev representing that device will get out of sync with the > > power.state of its ACPI companion object and that will lead to > > power management issues going forward. > > > > To avoid such issues it is better to leave the current_state value > > as is until it is changed to PCI_D0 by do_pci_enable_device() as > > appropriate. However, the power state of the device is not changed > > to PCI_D0 if it is already enabled when pci_enable_device_flags() > > gets called for it, so update its current_state in that case, but > > use pci_update_current_state() covering platform PM too for that. > > > > Link: https://lore.kernel.org/lkml/20210314000439.3138941-1-luzmaximilian@gmail.com/ > > Reported-by: Maximilian Luz > > Tested-by: Maximilian Luz > > Signed-off-by: Rafael J. Wysocki > > Bjorn, can I take this, or do you want to take care of it yourself? I'm taking the silence as consent, so the patch has been applied as 5.13 material with the R-by from Mika. > > --- > > > > Max, I've added a T-by from you even though the patch is slightly different > > from what you have tested, but the difference shouldn't matter for your case. > > > > --- > > drivers/pci/pci.c | 16 +++------------- > > 1 file changed, 3 insertions(+), 13 deletions(-) > > > > Index: linux-pm/drivers/pci/pci.c > > =================================================================== > > --- linux-pm.orig/drivers/pci/pci.c > > +++ linux-pm/drivers/pci/pci.c > > @@ -1870,20 +1870,10 @@ static int pci_enable_device_flags(struc > > int err; > > int i, bars = 0; > > > > - /* > > - * Power state could be unknown at this point, either due to a fresh > > - * boot or a device removal call. So get the current power state > > - * so that things like MSI message writing will behave as expected > > - * (e.g. if the device really is in D0 at enable time). > > - */ > > - if (dev->pm_cap) { > > - u16 pmcsr; > > - pci_read_config_word(dev, dev->pm_cap + PCI_PM_CTRL, &pmcsr); > > - dev->current_state = (pmcsr & PCI_PM_CTRL_STATE_MASK); > > - } > > - > > - if (atomic_inc_return(&dev->enable_cnt) > 1) > > + if (atomic_inc_return(&dev->enable_cnt) > 1) { > > + pci_update_current_state(dev, dev->current_state); > > return 0; /* already enabled */ > > + } > > > > bridge = pci_upstream_bridge(dev); > > if (bridge) > > > > > >