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From: Mika Westerberg <mika.westerberg@linux.intel.com>
To: Bjorn Helgaas <bhelgaas@google.com>,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Lukas Wunner <lukas@wunner.de>, David Airlie <airlied@linux.ie>,
	Daniel Vetter <daniel@ffwll.ch>,
	Utkarsh Patel <utkarsh.h.patel@intel.com>,
	Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
	Maxime Ripard <mripard@kernel.org>,
	Thomas Zimmermann <tzimmermann@suse.de>,
	linux-pci@vger.kernel.org,
	Mika Westerberg <mika.westerberg@linux.intel.com>
Subject: [PATCH] PCI/PM: Do not generate wakeup event when runtime resuming bus
Date: Thu, 29 Oct 2020 12:24:53 +0300	[thread overview]
Message-ID: <20201029092453.69869-1-mika.westerberg@linux.intel.com> (raw)

When a PCI bridge is runtime resumed from D3cold the underlying bus is
walked and the attached devices are runtime resumed as well. However, in
addition to that we also generate a wakeup event for these devices even
though this actually is not a real wakeup event coming from the
hardware.

Normally this does not cause problems but when combined with
/sys/power/wakeup_count like using the steps below:

  # count=$(cat /sys/power/wakeup_count)
  # echo $count > /sys/power/wakeup_count
  # echo mem > /sys/power/state

The system suspend cycle might get aborted at this point if a PCI bridge
that was runtime suspended (D3cold) was runtime resumed for any reason.
The runtime resume calls pci_wakeup_bus() and that generates wakeup
event increasing wakeup_count.

Since this is not a real wakeup event we can prevent the above from
happening by removing the call to pci_wakeup_event() in
pci_wakeup_bus(). While there rename pci_wakeup_bus() to
pci_resume_bus() to better reflect what it does.

Reported-by: Utkarsh Patel <utkarsh.h.patel@intel.com>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
---
 drivers/gpu/vga/vga_switcheroo.c |  2 +-
 drivers/pci/pci.c                | 16 +++++-----------
 include/linux/pci.h              |  2 +-
 3 files changed, 7 insertions(+), 13 deletions(-)

diff --git a/drivers/gpu/vga/vga_switcheroo.c b/drivers/gpu/vga/vga_switcheroo.c
index 087304b1a5d7..8843b078ad4e 100644
--- a/drivers/gpu/vga/vga_switcheroo.c
+++ b/drivers/gpu/vga/vga_switcheroo.c
@@ -1039,7 +1039,7 @@ static int vga_switcheroo_runtime_resume(struct device *dev)
 	mutex_lock(&vgasr_mutex);
 	vga_switcheroo_power_switch(pdev, VGA_SWITCHEROO_ON);
 	mutex_unlock(&vgasr_mutex);
-	pci_wakeup_bus(pdev->bus);
+	pci_resume_bus(pdev->bus);
 	ret = dev->bus->pm->runtime_resume(dev);
 	if (ret)
 		return ret;
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 6d4d5a2f923d..b25dfa63eeb9 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -1174,26 +1174,20 @@ int pci_platform_power_transition(struct pci_dev *dev, pci_power_t state)
 }
 EXPORT_SYMBOL_GPL(pci_platform_power_transition);
 
-/**
- * pci_wakeup - Wake up a PCI device
- * @pci_dev: Device to handle.
- * @ign: ignored parameter
- */
-static int pci_wakeup(struct pci_dev *pci_dev, void *ign)
+static int pci_resume_one(struct pci_dev *pci_dev, void *ign)
 {
-	pci_wakeup_event(pci_dev);
 	pm_request_resume(&pci_dev->dev);
 	return 0;
 }
 
 /**
- * pci_wakeup_bus - Walk given bus and wake up devices on it
+ * pci_resume_bus - Walk given bus and runtime resume devices on it
  * @bus: Top bus of the subtree to walk.
  */
-void pci_wakeup_bus(struct pci_bus *bus)
+void pci_resume_bus(struct pci_bus *bus)
 {
 	if (bus)
-		pci_walk_bus(bus, pci_wakeup, NULL);
+		pci_walk_bus(bus, pci_resume_one, NULL);
 }
 
 static int pci_dev_wait(struct pci_dev *dev, char *reset_type, int timeout)
@@ -1256,7 +1250,7 @@ int pci_power_up(struct pci_dev *dev)
 		 * may be powered on into D0uninitialized state, resume them to
 		 * give them a chance to suspend again
 		 */
-		pci_wakeup_bus(dev->subordinate);
+		pci_resume_bus(dev->subordinate);
 	}
 
 	return pci_raw_set_power_state(dev, PCI_D0);
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 22207a79762c..9256ef2e4327 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1271,7 +1271,7 @@ bool pci_dev_run_wake(struct pci_dev *dev);
 void pci_d3cold_enable(struct pci_dev *dev);
 void pci_d3cold_disable(struct pci_dev *dev);
 bool pcie_relaxed_ordering_enabled(struct pci_dev *dev);
-void pci_wakeup_bus(struct pci_bus *bus);
+void pci_resume_bus(struct pci_bus *bus);
 void pci_bus_set_current_state(struct pci_bus *bus, pci_power_t state);
 
 /* For use by arch with custom probe code */
-- 
2.28.0


             reply	other threads:[~2020-10-29  9:24 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-29  9:24 Mika Westerberg [this message]
2020-11-13  6:37 ` Mika Westerberg
2020-11-16 16:06   ` Rafael J. Wysocki
2020-11-16 16:05 ` Rafael J. Wysocki
2020-11-18 21:22 ` Bjorn Helgaas
2020-11-19  7:55   ` Mika Westerberg
2020-11-20  2:27     ` Patel, Utkarsh H

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