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 81305C433F5 for ; Tue, 9 Nov 2021 06:42:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5693B60F6E for ; Tue, 9 Nov 2021 06:42:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230150AbhKIGpF (ORCPT ); Tue, 9 Nov 2021 01:45:05 -0500 Received: from mail.kernel.org ([198.145.29.99]:32808 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229591AbhKIGpE (ORCPT ); Tue, 9 Nov 2021 01:45:04 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id E672660234; Tue, 9 Nov 2021 06:42:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1636440139; bh=B1IguEi2bwhHxjOBHleDUZl379REYQJYKiP/fzsjmag=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=p5J9N3GqT9v/BHqm+jT0fWwRW4bhsapm+tDX5PeGixFPln6G6/dPAP2jgByTNU2N8 K3ebZ/mnEy0PE/Yd2DAlh5GZIKHGqjIY6fJ+oq+2RtsxVaalciqNiJXVlEtYLMkQzH XXRbG/57WQZ3Hh/G1a3gZDhHPbpsMkYcrE14Bl58= Date: Tue, 9 Nov 2021 07:42:09 +0100 From: Greg Kroah-Hartman To: Bjorn Helgaas Cc: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= , Robert =?utf-8?B?xZp3acSZY2tp?= , linux-i2c@vger.kernel.org, Bjorn Helgaas , linux-pci@vger.kernel.org, "Rafael J. Wysocki" , linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] pci: Don't call resume callback for nearly bound devices Message-ID: References: <20211108212226.253mwl4wp7xjckqz@pengutronix.de> <20211109025619.GA1131403@bhelgaas> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20211109025619.GA1131403@bhelgaas> Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org On Mon, Nov 08, 2021 at 08:56:19PM -0600, Bjorn Helgaas wrote: > [+cc Greg: new device_is_bound() use] > > On Mon, Nov 08, 2021 at 10:22:26PM +0100, Uwe Kleine-König wrote: > > pci_pm_runtime_resume() exits early when the device to resume isn't > > bound yet: > > > > if (!to_pci_driver(dev->driver)) > > return 0; > > > > This however isn't true when the device currently probes and > > local_pci_probe() calls pm_runtime_get_sync() because then the driver > > core already setup dev->driver. As a result the driver's resume callback > > is called before the driver's probe function is called and so more often > > than not required driver data isn't setup yet. > > > > So replace the check for the device being unbound by a check that only > > becomes true after .probe() succeeded. > > I like the fact that this patch is short and simple. > > But there are 30+ users of to_pci_driver(). This patch asserts that > *one* of them, pci_pm_runtime_resume(), is special and needs to test > device_is_bound() instead of using to_pci_driver(). > > It's special because the current PM implementation calls it via > pm_runtime_get_sync() before the driver's .probe() method. That > connection is a little bit obscure and fragile. What if the PM > implementation changes? > > Maybe we just need a comment there about why it looks different than > the other PM interfaces? > > I also notice that the only other uses of device_is_bound() > outside the driver core are in iommu_group_store_type() and > regulator_resolve_supply(). This patch seems like a reasonable use, > but I always look twice when we do something unique. I agree that this looks really odd. No one should care outside of the driver core to call device_is_bound(), as if a driver is being called, implicitly you know that the device is bound to that driver. Why does the PCI core care if a device is bound to a pci driver at this point in time? But, this does feel like an odd use of to_pci_driver() here, what needs to be known here, if a pci driver is in control of a device here or not? thanks, greg k-h