From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932240AbcGTWql (ORCPT ); Wed, 20 Jul 2016 18:46:41 -0400 Received: from cloudserver094114.home.net.pl ([79.96.170.134]:43657 "HELO cloudserver094114.home.net.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1753633AbcGTWqj (ORCPT ); Wed, 20 Jul 2016 18:46:39 -0400 From: "Rafael J. Wysocki" To: Lukas Wunner Cc: Marek Szyprowski , "linux-pm@vger.kernel.org" , Linux Kernel Mailing List , "open list:AMD IOMMU (AMD-VI)" , linux-samsung-soc@vger.kernel.org, "linux-arm-kernel@lists.infradead.org" , Joerg Roedel , Inki Dae , Kukjin Kim , Krzysztof Kozlowski , Bartlomiej Zolnierkiewicz , Ulf Hansson , Mark Brown , Greg Kroah-Hartman , Andreas Noever , linux-pci@vger.kernel.org Subject: Re: [PATCH v2 02/10] driver core: Functional dependencies tracking support Date: Thu, 21 Jul 2016 00:51:31 +0200 Message-ID: <1735644.0mfUjJQtul@vostro.rjw.lan> User-Agent: KMail/4.11.5 (Linux/4.5.0-rc1+; KDE/4.11.5; x86_64; ; ) In-Reply-To: <20160720152340.GA8337@wunner.de> References: <1466144820-6286-1-git-send-email-m.szyprowski@samsung.com> <3969169.CcnEsvYuly@vostro.rjw.lan> <20160720152340.GA8337@wunner.de> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="utf-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wednesday, July 20, 2016 05:23:40 PM Lukas Wunner wrote: > On Wed, Jul 20, 2016 at 02:52:42PM +0200, Rafael J. Wysocki wrote: > > On Wednesday, July 20, 2016 08:24:50 AM Lukas Wunner wrote: > > > On Wed, Jul 20, 2016 at 02:33:18AM +0200, Rafael J. Wysocki wrote: > > > > On Friday, June 17, 2016 04:07:38 PM Lukas Wunner wrote: > > > > > On Fri, Jun 17, 2016 at 02:54:56PM +0200, Rafael J. Wysocki wrote: > > > > > > On Fri, Jun 17, 2016 at 12:36 PM, Lukas Wunner wrote: > > > > > > > On Fri, Jun 17, 2016 at 08:26:52AM +0200, Marek Szyprowski wrote: > > > > > > > > From: "Rafael J. Wysocki" > > > > > > > We also have such a functional dependency for Thunderbolt on Macs: > > > > > > > On resume from system sleep, the PCIe hotplug ports may not resume > > > > > > > before the thunderbolt driver has reestablished the PCI tunnels. > > > > > > > Currently this is enforced by quirk_apple_wait_for_thunderbolt() > > > > > > > in drivers/pci/quirks.c. It would be good if we could represent > > > > > > > this dependency using something like Rafael's approach instead of > > > > > > > open coding it, however one detail in Rafael's patches is problematic: > > > > > > > > > > > > > > > New links are added by calling device_link_add() which may happen > > > > > > > > either before the consumer device is probed or when probing it, in > > > > > > > > which case the caller needs to ensure that the driver of the > > > > > > > > supplier device is present and functional and the DEVICE_LINK_PROBE_TIME > > > > > > > > flag should be passed to device_link_add() to reflect that. > > > > > > > > > > > > > > The thunderbolt driver cannot call device_link_add() before the > > > > > > > PCIe hotplug ports are bound to a driver unless we amend portdrv > > > > > > > to return -EPROBE_DEFER for Thunderbolt hotplug ports on Macs > > > > > > > if the thunderbolt driver isn't loaded. > > > > > > > > > > > > > > It would therefore be beneficial if device_link_add() can be > > > > > > > called even *after* the consumer is bound. > > > > > > > > > > > > I don't quite follow. > > > > > > > > > > > > Who's the provider and who's the consumer here? > > > > > > > > > > thunderbolt.ko is the supplier. > > > > > > > > But it binds to the children of the ports that are supposed to be its > > > > consumers? > > > > > > > > Why is that even expected to work? > > > > > > No, the consumers are aunts (or uncles) of the supplier, if you will. :-) > > > > > > The consumers are the hotplug ports (named "Downstream Bridge 1 / 2" in > > > the drawing below). The supplier is the NHI: > > > > > > (Root Port) ---- Upstream Bridge --+-- Downstream Bridge 0 ---- NHI > > > +-- Downstream Bridge 1 -- > > > +-- Downstream Bridge 2 -- > > > ... > > > > > > We're calling pci_power_up() and pci_restore_state() from > > > pci_pm_resume_noirq(). And that will fail for devices below > > > the hotplug ports if the PCI tunnels haven't been re-established > > > yet by the NHI. > > > > So the NHI is a PCIe device, right? > > > > Does the Thunderbolt driver bind to that device? > > The NHI is a PCI device but not a bridge. It has class 0x88000. > Yes, thunderbolt.ko binds to the NHI. > > And portdrv binds to the upstream bridge and downstream bridges. > Those have class 0x60400. OK, so why would there be a problem with creating links from the NHI (producer) to the ports (consumers) before binding portdrv to them? Thanks, Rafael