linux-kernel - Re: [RESEND PATCH v3 1/2] PCI/PM: refactor pci_pm_suspend

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Date:   Tue, 30 Aug 2022 11:17:41 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     Rajvi Jingar <rajvi.jingar@...ux.intel.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Rafael Wysocki <rafael.j.wysocki@...el.com>,
        David Box <david.e.box@...ux.intel.com>,
        Linux PCI <linux-pci@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>
Subject: Re: [RESEND PATCH v3 1/2] PCI/PM: refactor pci_pm_suspend_noirq()

On Tue, Aug 30, 2022 at 01:44:43PM +0200, Rafael J. Wysocki wrote:
> Hi Bjorn,
> 
> On Tue, Aug 30, 2022 at 12:49 PM Rajvi Jingar
> <rajvi.jingar@...ux.intel.com> wrote:
> >
> > The state of the device is saved during pci_pm_suspend_noirq(), if it
> > has not already been saved, regardless of the skip_bus_pm flag value. So
> > skip_bus_pm check is removed before saving the device state.
> >
> > Signed-off-by: Rajvi Jingar <rajvi.jingar@...ux.intel.com>
> > Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> I have reviewed this and the [2/2] already and they are clear
> improvements to me.
> 
> Do you have any concerns regarding any of them?

Since the log doesn't mention fixing a problem, I guess this one is
only a simplification, right?  It looks functionally equivalent to me.

> If not, do you want me to pick them up or do you plan to take care of
> them yourself?

Let me take them; I want to at least wrap the comment to align with
the rest of the file.

> > ---
> >  v1->v2: no change
> >  v2->v3: no change

Why are we bumping the version numbers if there's truly no change?

> > ---
> >  drivers/pci/pci-driver.c | 18 ++++++------------
> >  1 file changed, 6 insertions(+), 12 deletions(-)
> >
> > diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
> > index 49238ddd39ee..1f64de3e5280 100644
> > --- a/drivers/pci/pci-driver.c
> > +++ b/drivers/pci/pci-driver.c
> > @@ -867,20 +867,14 @@ static int pci_pm_suspend_noirq(struct device *dev)
> >                 }
> >         }
> >
> > -       if (pci_dev->skip_bus_pm) {
> > +       if (!pci_dev->state_saved) {
> > +               pci_save_state(pci_dev);
> >                 /*
> > -                * Either the device is a bridge with a child in D0 below it, or
> > -                * the function is running for the second time in a row without
> > -                * going through full resume, which is possible only during
> > -                * suspend-to-idle in a spurious wakeup case.  The device should
> > -                * be in D0 at this point, but if it is a bridge, it may be
> > -                * necessary to save its state.
> > +                * If the device is a bridge with a child in D0 below it, it needs to
> > +                * stay in D0, so check skip_bus_pm to avoid putting it into a
> > +                * low-power state in that case.
> >                  */
> > -               if (!pci_dev->state_saved)
> > -                       pci_save_state(pci_dev);
> > -       } else if (!pci_dev->state_saved) {
> > -               pci_save_state(pci_dev);
> > -               if (pci_power_manageable(pci_dev))
> > +               if (!pci_dev->skip_bus_pm && pci_power_manageable(pci_dev))
> >                         pci_prepare_to_sleep(pci_dev);
> >         }
> >
> > --
> > 2.25.1
> >