On Tue, Apr 19, 2022 at 7:41 AM Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote:
>
> On Mon, Apr 18, 2022 at 02:00:45PM -0700, Evan Green wrote:
> > The PM_EVENT_FREEZE and PM_EVENT_QUIESCE messages should cause the
> > device to stop generating interrupts. USB core was previously allowing
> > devices that were already runtime suspended to keep remote wakeup
> > enabled if they had gone down that way. This violates the contract with
> > pm, and can potentially cause MSI interrupts to be lost.
> >
> > Change that so that if a device is runtime suspended with remote wakeups
> > enabled, it will be resumed to ensure remote wakeup is always disabled
> > across a freeze.
> >
> > Signed-off-by: Evan Green <evgreen@xxxxxxxxxxxx>
> > ---
> >
> > (no changes since v1)
> >
> > drivers/usb/core/driver.c | 20 +++++++++-----------
> > 1 file changed, 9 insertions(+), 11 deletions(-)
> >
> > diff --git a/drivers/usb/core/driver.c b/drivers/usb/core/driver.c
> > index 355ed33a21792b..93c8cf66adccec 100644
> > --- a/drivers/usb/core/driver.c
> > +++ b/drivers/usb/core/driver.c
> > @@ -1533,20 +1533,18 @@ static void choose_wakeup(struct usb_device *udev, pm_message_t msg)
> > {
> > int w;
> >
> > - /* Remote wakeup is needed only when we actually go to sleep.
> > - * For things like FREEZE and QUIESCE, if the device is already
> > - * autosuspended then its current wakeup setting is okay.
> > + /* For FREEZE/QUIESCE, disable remote wakeups so no interrupts get generated
> > + * by the device.
>
> You mean "by the host controller". USB devices don't generate
> interrupts; they generate wakeup requests (which can cause a host
> controller to generate an interrupt).
Right, I guess I mean "at the behest of the device". I could probably
just delete "by the device", since the goal of the comment is simply
to highlight that we're trying to kill interrupts, and describing
their provenance isn't as relevant.
>
> > */
> > if (msg.event == PM_EVENT_FREEZE || msg.event == PM_EVENT_QUIESCE) {
> > - if (udev->state != USB_STATE_SUSPENDED)
> > - udev->do_remote_wakeup = 0;
> > - return;
> > - }
> > + w = 0;
> >
> > - /* Enable remote wakeup if it is allowed, even if no interface drivers
> > - * actually want it.
> > - */
> > - w = device_may_wakeup(&udev->dev);
> > + } else {
> > + /* Enable remote wakeup if it is allowed, even if no interface drivers
> > + * actually want it.
> > + */
> > + w = device_may_wakeup(&udev->dev);
> > + }
> >
> > /* If the device is autosuspended with the wrong wakeup setting,
> > * autoresume now so the setting can be changed.
> > --
>
> I would prefer it if you reformatted the comments to agree with the
> current style:
>
> /*
> * Blah blah blah
> */
>
> and to avoid line wrap beyond 80 columns. Apart from that:
Sure, I can fix these up, add your tags, and repost.
>
> Acked-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
Thanks!
>
> Alan Stern
