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 EF8E8C433C1 for ; Mon, 22 Mar 2021 14:33:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AC4B56198E for ; Mon, 22 Mar 2021 14:33:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230266AbhCVOdS (ORCPT ); Mon, 22 Mar 2021 10:33:18 -0400 Received: from mail-ot1-f45.google.com ([209.85.210.45]:45707 "EHLO mail-ot1-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230494AbhCVOdN (ORCPT ); Mon, 22 Mar 2021 10:33:13 -0400 Received: by mail-ot1-f45.google.com with SMTP id f73-20020a9d03cf0000b02901b4d889bce0so16099029otf.12; Mon, 22 Mar 2021 07:33:13 -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=tdNjLAFkKExyySktCu7V5Bpz2cnyF7BEvssvzh+7BTo=; b=cx7fy9+H1Y4XBo0UIHXufE+9Znzedi5tZRFBVZ+VltucEbGIHDrsenB4E+SDvyRL2y K9GyKeAPSFB5IIfaQEd+MRAU4b71JCHIWp6YmIBs/P/aG9OpwXObsmVEhuKVY/84GwtG qtYXrWdvhUAqNUglIwApUMhR67NY8vVZQXyeJVJSK4C+IdmQ2a7sEp0TQkXfIG4XNOXI 7oqZVEWhW7w1kyLPYqg2WijKL2+Lw3gY5X8zXqqMIdwaKZlbZfk/k4dNV8ozOswJQ3w0 e10qkWmCNiRJ+ztSXWye5F8M1BVTE3V2VpKXfp3taxpxORaUHwP5QsLWnVUdNQhZJbhG xG7g== X-Gm-Message-State: AOAM532uiv+bW9VobhArHgxu73MHhpDICKpDbiTLAdLNZkZfVfA7wdxU MOPouJWn51iEq89R6/VxdtlEGQA0s18PMbMuHhw= X-Google-Smtp-Source: ABdhPJzkJoMaAR9z6HBKHF/TbDPxYzvAs7IoZZ69mFl3/xeSpEaCq/3dEr0P7DpmqDnhQnVarA9hGPOVdV3gBE4ynSA= X-Received: by 2002:a9d:4811:: with SMTP id c17mr233186otf.206.1616423593071; Mon, 22 Mar 2021 07:33:13 -0700 (PDT) MIME-Version: 1.0 References: <3219454.74lMxhSOWB@kreacher> In-Reply-To: <3219454.74lMxhSOWB@kreacher> From: "Rafael J. Wysocki" Date: Mon, 22 Mar 2021 15:32:58 +0100 Message-ID: Subject: Re: [PATCH] PCI: PM: Do not read power state in pci_enable_device_flags() To: Bjorn Helgaas Cc: 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 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? > --- > > 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) > > >