From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B08CB651AD; Tue, 19 Mar 2024 15:25:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710861915; cv=none; b=CBdvskjl6ILtvfURp+HTeQHxoVoNj+Z6NXOJvE0+DZLNebTFVCP9p754f3W4TAs5qOG/etiE1vMq2IZCWZgPzhJTQ++mIj8F3wgVDAavzW2O6gKoyjsbGRyHCrMb0HZEcx37LREBF0fjcSpcJOPluZOT0JOGWyRGflvLNmwilog= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710861915; c=relaxed/simple; bh=XgC+oIhFKtNDAik4l1Rt4yEt/LCvYMBQQFsAEqu4RWY=; h=Date:From:To:Cc:Subject:Message-ID:MIME-Version:Content-Type: Content-Disposition:In-Reply-To; b=MfApuk8iTsxJ0+mla1jcvLm+YdWuUsXPW041mHEuqQVqr3Zk/eFclJ2ai3VG150DBZEwJ/sZrIYIAF9kr3O39IsR0jvMfjT9oDcHbXB1TK7QKXZcbCzo3/UVtcrw87hC4dWeB+De4mGh7e439xMfbex8cbu9OLzhl3Q4xA64f0E= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=gNW3A9Xt; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="gNW3A9Xt" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E1445C433F1; Tue, 19 Mar 2024 15:25:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1710861915; bh=XgC+oIhFKtNDAik4l1Rt4yEt/LCvYMBQQFsAEqu4RWY=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=gNW3A9XtthFbAruB4DGpESZNAV1KN7mmlGxyiZZhLekabuNokSizuQkGZV6m12yhX 1aQeojCjTR+MblE2ZDWyqK6rS9/4vvZ8hFBkvmKInBQpuVZ1BdU0kSAYTbe4xe2GgP SyLuUeGLKpnezme4H8RyzHbyt3CYoJAvNF7SVxYBKf5CRnnrU8jC/9ykJzzmKf7MwD iqn+Gavfvn2TETe4YmigKmDmiJhoZUnr1rcxbCDm7ysQLf1KW0/sIXrfThdlIklqKx PwWA/TfLYmjZp+ZA3YjWlBfohdtpp7TYFsPE0mnuTOYht8IwvuL0IizcJii6QISu4h RXYl3H3Re8uXA== Date: Tue, 19 Mar 2024 10:25:13 -0500 From: Bjorn Helgaas To: Herve Codina Cc: Rob Herring , Greg Kroah-Hartman , "Rafael J. Wysocki" , Bjorn Helgaas , Lizhi Hou , Max Zhen , Sonal Santan , Stefano Stabellini , Jonathan Cameron , "linux-kernel@vger.kernel.org" , PCI , Allan Nielsen , Horatiu Vultur , Steen Hegelund , Thomas Petazzoni , Krzysztof =?utf-8?Q?Wilczy=C5=84ski?= Subject: Re: [PATCH v2 0/2] Attach DT nodes to existing PCI devices Message-ID: <20240319152513.GA1227721@bhelgaas> Precedence: bulk X-Mailing-List: linux-pci@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20231215145207.0cf098e5@bootlin.com> [+cc Krzysztof] On Fri, Dec 15, 2023 at 02:52:07PM +0100, Herve Codina wrote: > On Mon, 4 Dec 2023 07:59:09 -0600 > Rob Herring wrote: > > On Mon, Dec 4, 2023 at 6:43 AM Herve Codina wrote: > > > On Fri, 1 Dec 2023 16:26:45 -0600 > > > Rob Herring wrote: > > > > On Thu, Nov 30, 2023 at 10:57 AM Herve Codina wrote: > > > > ... > > > > --- a/drivers/pci/of.c > > > > +++ b/drivers/pci/of.c > > > > @@ -31,6 +31,8 @@ int pci_set_of_node(struct pci_dev *dev) > > > > return 0; > > > > > > > > node = of_pci_find_child_device(dev->bus->dev.of_node, dev->devfn); > > > > + if (!node && pci_is_bridge(dev)) > > > > + of_pci_make_dev_node(dev); > > > > if (!node) > > > > return 0; > > > > > > Maybe it is too early. > > > of_pci_make_dev_node() creates a node and fills some properties based on > > > some already set values available in the PCI device such as its struct resource > > > values. > > > We need to have some values set by the PCI infra in order to create our DT node > > > with correct values. > > > > Indeed, that's probably the issue I'm having. In that case, > > DECLARE_PCI_FIXUP_HEADER should work. That's later, but still before > > device_add(). > > > > I think modifying sysfs after device_add() is going to race with > > userspace. Userspace is notified of a new device, and then the of_node > > link may or may not be there when it reads sysfs. Also, not sure if > > we'll need DT modaliases with PCI devices, but they won't work if the > > DT node is not set before device_add(). > > DECLARE_PCI_FIXUP_HEADER is too early as well as doing the DT node creation > just before the device_add() call. > Indeed, in order to fill the DT properties, resources need to be assigned > (needed for the 'ranges' property used for addresses translation). > The resources assignment is done after the call to device_add(). Do we need to know the actual address *value* before creating the sysfs file, or is it enough to know that the file should *exist*, even if the value may be changed later? > Some PCI sysfs files are already created after adding the device by the > pci_create_sysfs_dev_files() call: > https://elixir.bootlin.com/linux/v6.6/source/drivers/pci/bus.c#L347 > > Is it really an issue to add the of_node link to sysfs on an already > present device ? Yes, I think this would be an issue. We've been trying to get rid of pci_create_sysfs_dev_files() altogether because there's a long history of race issues related to it: https://lore.kernel.org/r/1271099285.9831.13.camel@localhost/ WARNING: at fs/sysfs/dir.c:451 sysfs_add_one: sysfs: cannot create duplicate filename '/devices/pci0000:00/0000:00:01.0/slot' https://lore.kernel.org/r/19461.26166.427857.612983@pilspetsen.it.uu.se/ [2.6.35-rc1 regression] sysfs: cannot create duplicate filename ... XVR-600 related? https://lore.kernel.org/r/20200716110423.xtfyb3n6tn5ixedh@pali/ PCI: Race condition in pci_create_sysfs_dev_files https://lore.kernel.org/r/m3eebg9puj.fsf@t19.piap.pl/ PCI: Race condition in pci_create_sysfs_dev_files (can't boot) https://bugzilla.kernel.org/show_bug.cgi?id=215515 sysfs: cannot create duplicate filename '.../0000:e0' And several previous attempts to fix them: https://lore.kernel.org/r/4469eba2-188b-aab7-07d1-5c77313fc42f@gmail.com/ Guard pci_create_sysfs_dev_files with atomic value https://lore.kernel.org/r/20230316103036.1837869-1-alexander.stein@ew.tq-group.com PCI/sysfs: get rid of pci_sysfs_init late_initcall https://lore.kernel.org/r/1702093576-30405-1-git-send-email-ssengar@linux.microsoft.com/ PCI/sysfs: Fix race in pci sysfs creation Bjorn