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

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Date:   Tue, 2 Jul 2019 17:59:28 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        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 1, 2019 at 6:15 PM Mika Westerberg
<mika.westerberg@...ux.intel.com> wrote:
>
> 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

Thanks, I'll fix these up when applying the patch.