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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>,
	Mika Westerberg <mika.westerberg@linux.intel.com>,
	linux-pci@vger.kernel.org
Subject: [PATCH v2 1/2] PCI/PM: Do not generate wakeup event when runtime resuming bus
Date: Wed, 25 Nov 2020 12:07:32 +0300	[thread overview]
Message-ID: <20201125090733.77782-1-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 fail 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().

Reported-by: Utkarsh Patel <utkarsh.h.patel@intel.com>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
Previous version can be found here:

  https://www.spinics.net/lists/linux-pci/msg101083.html

Changes from the previous version:

  - Split the patch in two. The second patch only does the rename.
  - Tried to improve the commit message a bit
  - Added Rafael's reviewed-by tag

 drivers/pci/pci.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index e578d34095e9..6f7b33998fbe 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -1181,7 +1181,6 @@ EXPORT_SYMBOL_GPL(pci_platform_power_transition);
  */
 static int pci_wakeup(struct pci_dev *pci_dev, void *ign)
 {
-	pci_wakeup_event(pci_dev);
 	pm_request_resume(&pci_dev->dev);
 	return 0;
 }
-- 
2.29.2


             reply	other threads:[~2020-11-25  9:07 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-25  9:07 Mika Westerberg [this message]
2020-11-25  9:07 ` [PATCH v2 2/2] PCI: Rename pci_wakeup_bus() to pci_resume_bus() Mika Westerberg
2020-12-04 23:18 ` [PATCH v2 1/2] PCI/PM: Do not generate wakeup event when runtime resuming bus Bjorn Helgaas

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