Re: [PATCH] PCI / PM: Always check PME wakeup capability for runtime wakeup support

[Kai Heng Feng]

> On Mar 19, 2018, at 6:00 PM, Rafael J. Wysocki <rjw@xxxxxxxxxxxxx> wrote:
>
> On Sunday, March 18, 2018 8:12:15 PM CET Kai-Heng Feng wrote:
> > USB controller ASM1042 stops working after commit de3ef1eb1cd0 ("PM /
> > core: Drop run_wake flag from struct dev_pm_info").
> >
> > The device in question is not power managed by platform firmware,
> > furthermore, it only supports PME# from D3cold:
> > Capabilities: [78] Power Management version 3
> >        Flags: PMEClk- DSI- D1- D2- AuxCurrent=55mA PME(D0-,D1-,D2-,D3hot-,D3cold+)
> >        Status: D0 NoSoftRst+ PME-Enable- DSel=0 DScale=0 PME-
>
> That's somewhat unusual, but OK.
>
> > Before the commit, the device never gets runtime suspended. After the
> > commit, the device gets runtime suspended, so it does not respond to any
> > PME#.
> >
> > usb_hcd_pci_probe() mandatorily calls device_wakeup_enable(), hence
> > device_can_wakeup() in pci_dev_run_wake() always returns true.
> >
> > So pci_dev_run_wake() needs to check PME wakeup capability as its first
> > condition.
> >
> > Fixes: de3ef1eb1cd0 ("PM / core: Drop run_wake flag from struct  
> > dev_pm_info")
> > Cc: stable@xxxxxxxxxxxxxxx # 4.13+
> > Signed-off-by: Kai-Heng Feng <kai.heng.feng@xxxxxxxxxxxxx>
> > ---
> >  drivers/pci/pci.c | 11 ++++-------
> >  1 file changed, 4 insertions(+), 7 deletions(-)
> >
> > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> > index f6a4dd10d9b0..e026d8f313ec 100644
> > --- a/drivers/pci/pci.c
> > +++ b/drivers/pci/pci.c
> > @@ -2125,16 +2125,13 @@ bool pci_dev_run_wake(struct pci_dev *dev)
> >  {
> >  	struct pci_bus *bus = dev->bus;
> >
> > -	if (device_can_wakeup(&dev->dev))
> > -		return true;
> > -
> > -	if (!dev->pme_support)
> > -		return false;
>
> Why are you removing this check?

Because this is implicitly checked by pci_pme_capable().

But I guess it's better to keep it explicit.

I'll send a v2 to address this.

Kai-Heng

> > -
> >  	/* PME-capable in principle, but not from the target power state */
> > -	if (!pci_pme_capable(dev, pci_target_state(dev, false)))
> > +	if (!pci_pme_capable(dev, pci_target_state(dev, true)))
> >  		return false;
> >
> > +	if (device_can_wakeup(&dev->dev))
> > +		return true;
> > +
> >  	while (bus->parent) {
> >  		struct pci_dev *bridge = bus->self;
>
> Thanks,
> Rafael