On Thu, Sep 15, 2016 at 3:11 PM, Lukas Wunner <lukas@xxxxxxxxx> wrote:
> On Wed, Sep 14, 2016 at 02:29:52AM +0200, Rafael J. Wysocki wrote:
>> On Wednesday, August 31, 2016 08:15:18 AM Lukas Wunner wrote:
>> > We currently perform a mandatory runtime resume of all PCI devices on
>> > ->shutdown. However it is pointless to wake devices only to immediately
>> > power them down afterwards. (Or have the firmware reset them, in case
>> > of a reboot.)
>> >
>> > It seems there are only two cases when a runtime resume is actually
>> > necessary: If the driver has declared a ->shutdown callback or if kexec
>> > is in progress.
>> >
>> > Constrain resume of a device to these cases and let it slumber
>> > otherwise, thereby conserving energy and speeding up shutdown.
>> >
>> > Cc: Rafael J. Wysocki <rjw@xxxxxxxxxxxxx>
>> > Signed-off-by: Lukas Wunner <lukas@xxxxxxxxx>
>> > ---
>> > drivers/pci/pci-driver.c | 5 +++++
>> > 1 file changed, 5 insertions(+)
>> >
>> > diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
>> > index fd4b9c4..09a4e56 100644
>> > --- a/drivers/pci/pci-driver.c
>> > +++ b/drivers/pci/pci-driver.c
>> > @@ -459,6 +459,11 @@ static void pci_device_shutdown(struct device *dev)
>> > struct pci_dev *pci_dev = to_pci_dev(dev);
>> > struct pci_driver *drv = pci_dev->driver;
>> >
>> > + /* Fast path for suspended devices */
>> > + if (pm_runtime_suspended(dev) && (!drv || !drv->shutdown) &&
>> > + !kexec_in_progress)
>>
>> What happens if runtime suspend or resume of the device happens here?
>
> You're right, good point. How about disabling runtime PM then, like this:
>
> /* Fast path for suspended devices */
> if (pm_runtime_status_suspended(dev) && (!drv || !drv->shutdown) &&
> !kexec_in_progress) {
> pm_runtime_disable(dev);
> if (pm_runtime_status_suspended(dev))
> return;
> pm_runtime_enable(dev);
> }
>
> All dependents (children, and in the future, consumers) should already
> have been treated at that point, due to the ordering of devices_kset->list.
That should work.
Thanks,
Rafael
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