linux-kernel - Re: [PATCH v2 1/5] PM: ACPI/PCI: Resume all devices during hibernation

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Date:   Mon, 1 Jul 2019 19:15:50 +0300
From:   Mika Westerberg <mika.westerberg@...ux.intel.com>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     Linux PM <linux-pm@...r.kernel.org>,
        Linux PCI <linux-pci@...r.kernel.org>,
        Linux ACPI <linux-acpi@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Bjorn Helgaas <helgaas@...nel.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Hans De Goede <hdegoede@...hat.com>,
        "Robert R. Howell" <RHowell@...o.edu>
Subject: Re: [PATCH v2 1/5] PM: ACPI/PCI: Resume all devices during
 hibernation

On Mon, Jul 01, 2019 at 12:44:25PM +0200, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> Both the PCI bus type and the ACPI PM domain avoid resuming
> runtime-suspended devices with DPM_FLAG_SMART_SUSPEND set during
> hibernation (before creating the snapshot image of system memory),
> but that turns out to be a mistake.  It leads to functional issues
> and adds complexity that's hard to justify.
> 
> For this reason, resume all runtime-suspended PCI devices and all
> devices in the ACPI PM domains before creating a snapshot image of
> system memory during hibernation.
> 
> Fixes: 05087360fd7a (ACPI / PM: Take SMART_SUSPEND driver flag into account)
> Fixes: c4b65157aeef (PCI / PM: Take SMART_SUSPEND driver flag into account)
> Link: https://lore.kernel.org/linux-acpi/917d4399-2e22-67b1-9d54-808561f9083f@uwyo.edu/T/#maf065fe6e4974f2a9d79f332ab99dfaba635f64c
> Reported-by: Robert R. Howell <RHowell@...o.edu>
> Tested-by: Robert R. Howell <RHowell@...o.edu>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
> 
> -> v2: No changes.
> 
> ---
>  drivers/acpi/device_pm.c |   13 +++++++------
>  drivers/pci/pci-driver.c |   16 ++++++++--------
>  2 files changed, 15 insertions(+), 14 deletions(-)
> 
> Index: linux-pm/drivers/acpi/device_pm.c
> ===================================================================
> --- linux-pm.orig/drivers/acpi/device_pm.c
> +++ linux-pm/drivers/acpi/device_pm.c
> @@ -1155,13 +1155,14 @@ EXPORT_SYMBOL_GPL(acpi_subsys_resume_ear
>  int acpi_subsys_freeze(struct device *dev)
>  {
>  	/*
> -	 * This used to be done in acpi_subsys_prepare() for all devices and
> -	 * some drivers may depend on it, so do it here.  Ideally, however,
> -	 * runtime-suspended devices should not be touched during freeze/thaw
> -	 * transitions.
> +	 * Resume all runtime-suspended devices before creating a snapshot
> +	 * image of system memory, because the restore kernel generally cannot
> +	 * be expected to always handle them consistently and they need to be
> +	 * put into the runtime-active metastate during system resume anyway,
> +	 * so it is better to ensure that the state saved in the image will be
> +	 * alwyas consistent with that.

alwyas -> always

>  	 */
> -	if (!dev_pm_test_driver_flags(dev, DPM_FLAG_SMART_SUSPEND))
> -		pm_runtime_resume(dev);
> +	pm_runtime_resume(dev);
>  
>  	return pm_generic_freeze(dev);
>  }
> Index: linux-pm/drivers/pci/pci-driver.c
> ===================================================================
> --- linux-pm.orig/drivers/pci/pci-driver.c
> +++ linux-pm/drivers/pci/pci-driver.c
> @@ -1012,15 +1012,15 @@ static int pci_pm_freeze(struct device *
>  	}
>  
>  	/*
> -	 * This used to be done in pci_pm_prepare() for all devices and some
> -	 * drivers may depend on it, so do it here.  Ideally, runtime-suspended
> -	 * devices should not be touched during freeze/thaw transitions,
> -	 * however.
> +	 * Resume all runtime-suspended devices before creating a snapshot
> +	 * image of system memory, because the restore kernel generally cannot
> +	 * be expected to always handle them consistently and they need to be
> +	 * put into the runtime-active metastate during system resume anyway,
> +	 * so it is better to ensure that the state saved in the image will be
> +	 * alwyas consistent with that.

ditto

>  	 */
> -	if (!dev_pm_smart_suspend_and_suspended(dev)) {
> -		pm_runtime_resume(dev);
> -		pci_dev->state_saved = false;
> -	}
> +	pm_runtime_resume(dev);
> +	pci_dev->state_saved = false;
>  
>  	if (pm->freeze) {
>  		int error;
> 
> 
>