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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B2F02C43217 for ; Wed, 10 Nov 2021 14:14:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 94938610A8 for ; Wed, 10 Nov 2021 14:14:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232143AbhKJORa (ORCPT ); Wed, 10 Nov 2021 09:17:30 -0500 Received: from mail.kernel.org ([198.145.29.99]:36682 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231607AbhKJOR3 (ORCPT ); Wed, 10 Nov 2021 09:17:29 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 536C8610CF; Wed, 10 Nov 2021 14:14:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1636553681; bh=ULssGWa9GKLPoBBHvT9SZdMTkwJdbGAWdXOkGpY4kkc=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=knfAa4ESl4Ws/Ll++SyVhZfck9pYKkVkJUlFPDpi0DzFMPBbj7hxEsIwpXxsjXj55 kgpxs1ATu1nRh4EYPI4v0MFtJRAp6Kj1sjvAXXj6tipQifxyBxJKri56MsnzIc8SWE P0fnTWXqgTO0JCVqLlxyEZejU5tNF1mIsQm4+4sGW8Ab0h5M0IKUlWBaz2EljopmxK ha9rBeOeteZt1DC8wDEhHoFaMitgM0c7BirhK3NiKY2ttbXcuCTHQiIfAFvXqX1tbg 0RQTcZ5iVZK2bUAYuAbCUghnVmk9zjuqTYVSfeVQGh2Tbaq9lSXCZCCglKxsKPOcdG hY0rrWvi5u6pg== Date: Wed, 10 Nov 2021 08:14:39 -0600 From: Bjorn Helgaas To: Robert =?utf-8?B?xZp3acSZY2tp?= Cc: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= , linux-i2c , Bjorn Helgaas , Linux PCI , Linux PM , Linux Kernel Mailing List , Greg Kroah-Hartman , "Rafael J. Wysocki" Subject: Re: [PATCH] pci: Don't call resume callback for nearly bound devices Message-ID: <20211110141439.GA1240945@bhelgaas> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20211109200518.GA1176309@bhelgaas> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 09, 2021 at 02:05:18PM -0600, Bjorn Helgaas wrote: > On Tue, Nov 09, 2021 at 07:58:47PM +0100, Rafael J. Wysocki wrote: > > On Tue, Nov 9, 2021 at 7:52 PM Rafael J. Wysocki wrote: > > > ... > > > So instead, we can drop the pm_runtime_get_sync() and > > > pm_runtime_put_sync() from local_pci_probe() and pci_device_remove(), > > > respectively, and add pm_runtine_get_noresume() to pci_pm_init(), > > > which will prevent PM-runtime from touching the device until it has a > > > driver that supports PM-runtime. > > > > > > We'll lose the theoretical ability to put unbound devices into D3 this > > > way, but we learned some time ago that this isn't safe in all cases > > > anyway. > > > > IOW, something like this (untested and most likely white-space-damaged). > > Thanks! I applied this manually to for-linus in hopes of making the > the next linux-next build. > > Please send any testing reports and corrections to the patch and > commit log! Robert, I hate to ask even more of you, but if you have a chance, it would be very helpful if you could test the patch below. I'm pretty sure it should fix the problem you saw, and I hope to ask Linus to merge it today. > commit dd414877b58b ("PCI/PM: Prevent runtime PM until claimed by a driver that supports it") > Author: Bjorn Helgaas > Date: Tue Nov 9 13:36:09 2021 -0600 > > PCI/PM: Prevent runtime PM until claimed by a driver that supports it > > Previously we had a path that could call a driver's ->runtime_resume() > method before calling the driver's ->probe() method, which is a problem > because ->runtime_resume() often relies on initialization done in > ->probe(): > > local_pci_probe > pm_runtime_get_sync > ... > pci_pm_runtime_resume > if (!pci_dev->driver) > return 0; <-- early exit > dev->driver->pm->runtime_resume(); <-- driver ->runtime_resume() > pci_dev->driver = pci_drv; > pci_drv->probe() <-- driver ->probe() > > Prior to 2a4d9408c9e8 ("PCI: Use to_pci_driver() instead of > pci_dev->driver"), we took the early exit, which avoided the problem. But > 2a4d9408c9e8 removed pci_dev->driver (since it's redundant with > device->driver), so we no longer take the early exit, which leads to havoc > in ->runtime_resume(). > > Similarly, we could call the driver's ->runtime_idle() method after its > ->remove() method. > > Avoid the problem by dropping the pm_runtime_get_sync() and > pm_runtime_put_sync() from local_pci_probe() and pci_device_remove(), > respectively. > > Add pm_runtime_get_noresume(), which uses no driver PM callbacks, to the > pci_pm_init() enumeration path. This will prevent PM-runtime from touching > the device until it has a driver that supports PM-runtime. > > Link: https://lore.kernel.org/r/CAJZ5v0impb8uscbp8LUTBMExfMoGz=cPrTWhSGh0GF_SANNKPQ@mail.gmail.com > Fixes: 2a4d9408c9e8 ("PCI: Use to_pci_driver() instead of pci_dev->driver") > Reported-by: Robert Święcki > Suggested-by: Rafael J. Wysocki > Signed-off-by: Bjorn Helgaas > > diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c > index 1d98c974381c..41cdf510214f 100644 > --- a/drivers/pci/pci-driver.c > +++ b/drivers/pci/pci-driver.c > @@ -309,16 +309,6 @@ static long local_pci_probe(void *_ddi) > struct device *dev = &pci_dev->dev; > int rc; > > - /* > - * Unbound PCI devices are always put in D0, regardless of > - * runtime PM status. During probe, the device is set to > - * active and the usage count is incremented. If the driver > - * supports runtime PM, it should call pm_runtime_put_noidle(), > - * or any other runtime PM helper function decrementing the usage > - * count, in its probe routine and pm_runtime_get_noresume() in > - * its remove routine. > - */ > - pm_runtime_get_sync(dev); > rc = pci_drv->probe(pci_dev, ddi->id); > if (!rc) > return rc; > @@ -464,9 +454,6 @@ static void pci_device_remove(struct device *dev) > pcibios_free_irq(pci_dev); > pci_iov_remove(pci_dev); > > - /* Undo the runtime PM settings in local_pci_probe() */ > - pm_runtime_put_sync(dev); > - > /* > * If the device is still on, set the power state as "unknown", > * since it might change by the next time we load the driver. > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c > index b88db815ee01..e9c38b994c73 100644 > --- a/drivers/pci/pci.c > +++ b/drivers/pci/pci.c > @@ -3097,7 +3097,15 @@ void pci_pm_init(struct pci_dev *dev) > u16 pmc; > > pm_runtime_forbid(&dev->dev); > + > + /* > + * Unbound PCI devices are always put in D0. If the driver supports > + * runtime PM, it should call pm_runtime_put_noidle(), or any other > + * runtime PM helper function decrementing the usage count, in its > + * probe routine and pm_runtime_get_noresume() in its remove routine. > + */ > pm_runtime_set_active(&dev->dev); > + pm_runtime_get_noresume(&dev->dev); > pm_runtime_enable(&dev->dev); > device_enable_async_suspend(&dev->dev); > dev->wakeup_prepared = false;