Re: Linux 4.15-rc2: Regression in resume from ACPI S3

[Rafael J. Wysocki]

On Thursday, December 14, 2017 1:30:37 PM CET Thomas Gleixner wrote:
> On Thu, 14 Dec 2017, Rafael J. Wysocki wrote:
> > On Thursday, December 14, 2017 12:54:05 PM CET Thomas Gleixner wrote:
> > > Now the graphics issue is a different story. That only happens on
> > > hibernation after doing the snapshot. There all non boot cpus are onlined
> > > again and after that the devices are 'thawed'. The following reenable of
> > > interrupts fails because i915 is not in PCI_D0 state.
> > > 
> > > Suspend:
> > > 
> > >    irq_migrate_all_off_this_cpu: Mask 125 pci_msi_mask_irq+0x0/0x10
> > >    __pci_write_msi_msg: 0000:00:02.0 00000000fee0100c 0000412a
> > >    __pci_write_msi_msg: Not written <- Device not in PCI_D0
> > >    ....
> > >    device_pm_callback_start: i915 0000:00:02.0, parent: pci0000:00, noirq bus [resume]
> > >    pci_pm_resume_noirq <-dpm_run_callback
> > >    pci_pm_resume_noirq <-dpm_run_callback
> > >    pci_pm_default_resume_early <-pci_pm_resume_noirq
> > >    pci_pm_default_resume_early <-pci_pm_resume_noirq
> > >    __pci_write_msi_msg: 0000:00:02.0 00000000fee0100c 0000412a  <-- Set the new affinity
> > >    device_pm_callback_end: i915 0000:00:02.0, err=0
> > 
> > So this works, because we power up the device during resume even if it
> > had been suspended (via runtime PM) before the suspend started.
> > 
> > > Hibernate:
> > > 
> > >    irq_migrate_all_off_this_cpu: Mask 125 pci_msi_mask_irq+0x0/0x10
> > >    __pci_write_msi_msg: 0000:00:02.0 00000000fee0100c 0000412a
> > >    __pci_write_msi_msg: Not written <- Device not in PCI_D0
> > >    ....
> > >    device_pm_callback_start: i915 0000:00:02.0, parent: pci0000:00, noirq bus [thaw]
> > >    pci_pm_thaw_noirq <-dpm_run_callback
> > >    __pci_write_msi_msg: 0000:00:02.0 00000000fee0100c 0000412a
> > >    __pci_write_msi_msg: Not written  <--- Device is not in PCI_D0
> > >    device_pm_callback_end: i915 0000:00:02.0, err=0
> > 
> > And here we try to leave the device alone which is OK for devices in D0,
> > but not for suspended ones.
> > 
> > It looks like we need to power up them at the "thaw" time too or at least
> > I don't see how to address that differently.
> 
> The question is whether the code which brings the device out of D0 should
> write the message unconditionally. That would be sufficient I think.

It doesn't have to do that.

The problem here is that pci_pm_thaw_noirq() calls pci_restore_state() which
in fact requires the device to be in D0, so the caller should put it into
D0 instead of trying to "update" its power state.

[Note that the PCI layer doesn't put devices into low-power states during the
hibernation's "freeze" transition, but drivers can legitimately do that in
their "freeze" callbacks which was overlooked in that code and that's what
i915 does.]

So IMO what we need is the change below.  I'm going to test it shortly,
but please give it a go too.

---
 drivers/pci/pci-driver.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

Index: linux-pm/drivers/pci/pci-driver.c
===================================================================
--- linux-pm.orig/drivers/pci/pci-driver.c
+++ linux-pm/drivers/pci/pci-driver.c
@@ -1027,7 +1027,12 @@ static int pci_pm_thaw_noirq(struct devi
 	if (pci_has_legacy_pm_support(pci_dev))
 		return pci_legacy_resume_early(dev);
 
-	pci_update_current_state(pci_dev, PCI_D0);
+	/*
+	 * pci_restore_state() requires the device to be in D0 (because of MSI
+	 * restoration among other things), so force it into D0 in case the
+	 * driver's "freeze" callbacks put it into a low-power state directly.
+	 */
+	pci_set_power_state(pci_dev, PCI_D0);
 	pci_restore_state(pci_dev);
 
 	if (drv && drv->pm && drv->pm->thaw_noirq)