Re: [PATCH v2 1/2] PCI/PM: Do not generate wakeup event when runtime resuming bus

From: Bjorn Helgaas <helgaas@kernel.org>
To: Mika Westerberg <mika.westerberg@linux.intel.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>,
	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
Subject: Re: [PATCH v2 1/2] PCI/PM: Do not generate wakeup event when runtime resuming bus
Date: Fri, 4 Dec 2020 17:18:03 -0600	[thread overview]
Message-ID: <20201204231803.GA1980572@bjorn-Precision-5520> (raw)
In-Reply-To: <20201125090733.77782-1-mika.westerberg@linux.intel.com>

On Wed, Nov 25, 2020 at 12:07:32PM +0300, Mika Westerberg wrote:
> 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>

I reversed the order of these since I think it's more obvious that
pci_wakeup_event() doesn't fit in pci_resume_one() and applied both to
pci/pm for v5.11, thanks!

> ---
> 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
> 