On Mon, Apr 23, 2018 at 09:43:52AM +0200, Rafael J. Wysocki wrote:
> On Friday, April 20, 2018 2:22:02 PM CEST Mika Westerberg wrote:
> > If a driver uses DPM_FLAG_SMART_SUSPEND and the device is already
> > runtime suspended when hibernate is started PCI core skips runtime
> > resuming the device but still clears pci_dev->state_saved. After the
> > hibernation image is written pci_pm_thaw_noirq() makes sure subsequent
> > thaw phases for the device are also skipped leaving it runtime suspended
> > with pci_dev->state_saved == false.
> >
> > When the device is eventually runtime resumed pci_pm_runtime_resume()
> > restores config space by calling pci_restore_standard_config(), however
> > because pci_dev->state_saved == false pci_restore_state() never actually
> > restores the config space leaving the device in a state that is not what
> > the driver might expect.
> >
> > For example here is what happens for intel-lpss I2C devices once the
> > hibernation snapshot is taken:
> >
> > intel-lpss 0000:00:15.0: power state changed by ACPI to D0
> > intel-lpss 0000:00:1e.0: power state changed by ACPI to D3cold
> > video LNXVIDEO:00: Restoring backlight state
> > PM: hibernation exit
> > i2c_designware i2c_designware.1: Unknown Synopsys component type: 0xffffffff
> > i2c_designware i2c_designware.0: Unknown Synopsys component type: 0xffffffff
> > i2c_designware i2c_designware.1: timeout in disabling adapter
> > i2c_designware i2c_designware.0: timeout in disabling adapter
> >
> > Since PCI config space is not restored the device is still in D3hot
> > making MMIO register reads return 0xffffffff.
> >
> > Fix this by clearing pci_dev->state_saved only if we actually end up
> > runtime resuming the device.
> >
> > Fixes: c4b65157aeef ("PCI / PM: Take SMART_SUSPEND driver flag into account")
> > Signed-off-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
>
> Since this fixes a commit that went in through the PM tree, I've queued it up.
>
> Bjorn, please let me know if you prefer to route it through the PCI tree.
Thanks for taking it, that's perfect!
> > ---
> > drivers/pci/pci-driver.c | 5 +++--
> > 1 file changed, 3 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
> > index 6ace47099fc5..b9a131137e64 100644
> > --- a/drivers/pci/pci-driver.c
> > +++ b/drivers/pci/pci-driver.c
> > @@ -958,10 +958,11 @@ static int pci_pm_freeze(struct device *dev)
> > * devices should not be touched during freeze/thaw transitions,
> > * however.
> > */
> > - if (!dev_pm_test_driver_flags(dev, DPM_FLAG_SMART_SUSPEND))
> > + if (!dev_pm_smart_suspend_and_suspended(dev)) {
> > pm_runtime_resume(dev);
> > + pci_dev->state_saved = false;
> > + }
> >
> > - pci_dev->state_saved = false;
> > if (pm->freeze) {
> > int error;
> >
> >
>
>
