Date:	Wed, 15 Apr 2015 19:01:06 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Bjorn Helgaas <bhelgaas@...gle.com>
Cc:	"Rafael J. Wysocki" <rafael@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linux PCI <linux-pci@...r.kernel.org>,
	Henrique de Moraes Holschuh <hmh@....eng.br>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	tiagdtd-lava <tiagdtd-lava@...oo.de>
Subject: Re: [PATCH] PCI / hotplug: Propagate the "ignore hotplug" setting to parent

On Wednesday, April 15, 2015 05:36:42 PM Rafael J. Wysocki wrote:
> On Apr 15, 2015 3:16 PM, "Rafael J. Wysocki" <rafael@...nel.org> wrote:
> >
> > On Wed, Apr 15, 2015 at 2:55 PM, Bjorn Helgaas <bhelgaas@...gle.com>
> wrote:
> > > On Tue, Apr 14, 2015 at 8:03 PM, Rafael J. Wysocki <rjw@...ysocki.net>
> wrote:
> > >> On Tuesday, April 14, 2015 12:28:12 PM Henrique de Moraes Holschuh
> wrote:
> > >>> On Mon, Apr 13, 2015, at 11:23, Rafael J. Wysocki wrote:
> > >>> > From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > >>> >
> > >>> > Refine the mechanism introduced by commit f244d8b623da (ACPIPHP /
> radeon
> > >>> > / nouveau: Fix VGA switcheroo problem related to hotplug) to
> propagate
> > >>> > the ignore_hotplug setting of the device to its parent bridge in
> case
> > >>> > hotplug notifications related to the graphics adapter switching are
> > >>> > given for the bridge rather than for the device itself (the need to
> > >>> > be ignored in both cases).
> > >>>
> > >>> I do apologise if this is a stupid question, but is there any chance
> the
> > >>> bridge will be connected to other devices that do require hotplug
> handling,
> > >>> and not just to the GPU?
> > >>
> > >> The bridge is actually a downstream PCIe port holding the GPU, so no.
> :-)
> > >
> > > When radeon/nouveau call pci_ignore_hotplug(), that's the case, but in
> > > general all we know is that pci_ignore_hotplug() receives a PCI
> > > device.  We don't know whether it's PCI or PCIe.  In the hotplug
> > > topologies I'm familiar with, a bridge only leads to one hot-pluggable
> > > slot, but I don't remember anything that would guarantee that.  For
> > > PCIe, I think there can only be one slot, but for PCI I would think it
> > > possible to have one bridge leading to several hotpluggable slots,
> > > with the hotplug controller(s) being separate from the bridge.
> >
> > Realistically, the switcheroo people are the only users of
> > pci_ignore_hotplug() today and if somebody wants the hotplug events to
> > be ignored for him and perhaps not for someone else on the same
> > bridge, then something is seriously broken about that system anyway.
> 
> There may be a problem if somebody *already* calls this function for the
> parent bridge (which some callers do ISTR) in which case the setting will
> be propagated unnecessarily.
> 
> That said, since all of the existing callers of pci_ignore_hotplug() appear
> to need to set the flag for the parent too, IMO it's better to put that
> logic into the interface instead of duplicating it in the callers. So, why
> don't we add a second argument indicating whether or not to propagate the
> setting?

My previous message didn't seem to reach the mailing lists, so above is a
quote from it and below is a new version of the patch with the additional
argument to pci_ignore_hotplug().

Rafael


---
From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Subject: PCI / hotplug: Propagate the "ignore hotplug" setting to parent

Refine the mechanism introduced by commit f244d8b623da (ACPIPHP / radeon
/ nouveau: Fix VGA switcheroo problem related to hotplug) to optionally
propagate the ignore_hotplug setting of the device to its parent bridge
in case hotplug notifications related to the graphics adapter switching
are given for the bridge rather than for the device itself (the need to
be ignored in both cases).

Link: https://bugzilla.kernel.org/show_bug.cgi?id=61891
Link: https://bugs.freedesktop.org/show_bug.cgi?id=88927
Reported-by: tiagdtd-lava <tiagdtd-lava@...oo.de>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---
 drivers/gpu/drm/nouveau/nouveau_drm.c |    2 +-
 drivers/gpu/drm/radeon/radeon_drv.c   |    2 +-
 drivers/pci/pci.c                     |   16 ++++++++++++++++
 include/linux/pci.h                   |    6 +-----
 4 files changed, 19 insertions(+), 7 deletions(-)

Index: linux-pm/drivers/pci/pci.c
===================================================================
--- linux-pm.orig/drivers/pci/pci.c
+++ linux-pm/drivers/pci/pci.c
@@ -4319,6 +4319,22 @@ bool pci_device_is_present(struct pci_de
 }
 EXPORT_SYMBOL_GPL(pci_device_is_present);
 
+/**
+ * pci_ignore_hotplug - Ignore subsequent hotplug notifies for this device.
+ * @dev: Target device.
+ * @propagate: Whether or not to ignore hotplug notifies for the parent bridge.
+ */
+void pci_ignore_hotplug(struct pci_dev *dev, bool propagate)
+{
+	struct pci_dev *bridge = dev->bus->self;
+
+	dev->ignore_hotplug = 1;
+	/* Propagate the "ignore hotplug" setting to the parent bridge. */
+	if (bridge && propagate)
+		bridge->ignore_hotplug = 1;
+}
+EXPORT_SYMBOL_GPL(pci_ignore_hotplug);
+
 #define RESOURCE_ALIGNMENT_PARAM_SIZE COMMAND_LINE_SIZE
 static char resource_alignment_param[RESOURCE_ALIGNMENT_PARAM_SIZE] = {0};
 static DEFINE_SPINLOCK(resource_alignment_lock);
Index: linux-pm/include/linux/pci.h
===================================================================
--- linux-pm.orig/include/linux/pci.h
+++ linux-pm/include/linux/pci.h
@@ -1002,6 +1002,7 @@ int __must_check pci_assign_resource(str
 int __must_check pci_reassign_resource(struct pci_dev *dev, int i, resource_size_t add_size, resource_size_t align);
 int pci_select_bars(struct pci_dev *dev, unsigned long flags);
 bool pci_device_is_present(struct pci_dev *pdev);
+void pci_ignore_hotplug(struct pci_dev *dev, bool propagate);
 
 /* ROM control related routines */
 int pci_enable_rom(struct pci_dev *pdev);
@@ -1039,11 +1040,6 @@ bool pci_dev_run_wake(struct pci_dev *de
 bool pci_check_pme_status(struct pci_dev *dev);
 void pci_pme_wakeup_bus(struct pci_bus *bus);
 
-static inline void pci_ignore_hotplug(struct pci_dev *dev)
-{
-	dev->ignore_hotplug = 1;
-}
-
 static inline int pci_enable_wake(struct pci_dev *dev, pci_power_t state,
 				  bool enable)
 {
Index: linux-pm/drivers/gpu/drm/nouveau/nouveau_drm.c
===================================================================
--- linux-pm.orig/drivers/gpu/drm/nouveau/nouveau_drm.c
+++ linux-pm/drivers/gpu/drm/nouveau/nouveau_drm.c
@@ -731,7 +731,7 @@ nouveau_pmops_runtime_suspend(struct dev
 	ret = nouveau_do_suspend(drm_dev, true);
 	pci_save_state(pdev);
 	pci_disable_device(pdev);
-	pci_ignore_hotplug(pdev);
+	pci_ignore_hotplug(pdev, true);
 	pci_set_power_state(pdev, PCI_D3cold);
 	drm_dev->switch_power_state = DRM_SWITCH_POWER_DYNAMIC_OFF;
 	return ret;
Index: linux-pm/drivers/gpu/drm/radeon/radeon_drv.c
===================================================================
--- linux-pm.orig/drivers/gpu/drm/radeon/radeon_drv.c
+++ linux-pm/drivers/gpu/drm/radeon/radeon_drv.c
@@ -453,7 +453,7 @@ static int radeon_pmops_runtime_suspend(
 	ret = radeon_suspend_kms(drm_dev, false, false);
 	pci_save_state(pdev);
 	pci_disable_device(pdev);
-	pci_ignore_hotplug(pdev);
+	pci_ignore_hotplug(pdev, true);
 	pci_set_power_state(pdev, PCI_D3cold);
 	drm_dev->switch_power_state = DRM_SWITCH_POWER_DYNAMIC_OFF;
 

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