On Wed, 26 Jun 2013, Roger Quadros wrote:
> > Could the mapping be changed so that a different interrupt vector was
> > used for wakeups and normal I/O? That would make this a little easier,
> > although it wouldn't solve the general problem.
>
> I'm not sure which IRQ we can map it to, but it could be mapped to some
> free IRQ number. Since it doesn't make things easier, I think we can leave
> it as it is for now.
All right.
> > There's still a race problem. Suppose a normal wakeup interrupt occurs
> > just before or as the controller gets suspended. By the time the code
> > here runs, HCD_HW_ACCESSIBLE may have been cleared by the suspend
> > routine. The interrupt would be lost. Depending on the design of the
> > controller, the entire wakeup signal could end up getting lost as well.
>
> But if I call ehci_suspend() in the runtime_suspend handler, this race
> won't happen right?
That race doesn't apply to your system anyway; it matters only on
systems where hcd->has_wakeup_irq isn't set. The only way to fix it
involves changing ehci_suspend() somewhat (and making the equivalent
change for other HCDs too). Those musings above were just me thinking
out loud about the problems involved in implementing reliable wakeups.
> > Do you know how the OMAP EHCI controller behaves? Under what
> > conditions does it send the wakeup IRQ? How do you tell it to turn off
> > the wakeup IRQ?
>
> Once the controller is suspended, the wakeup IRQ comes out-of-band. i.e. through
> pad wakeup and pinctrl subsystem.
> The only way to turn that wakeup off is to disable the wakeup enable bit on the pad.
> This could be done by not putting the pins in the IDLE_WAKEUP state during
> suspend.
That's not what I meant. Never mind the pinctrl; I was asking about
the EHCI controller itself. Under what circumstances does the
controller assert its wakeup signal? And how do you tell it to stop
asserting that signal?
> Thanks for the review.
>
> I updated the ehci-omap.c driver to call ehci_suspend/resume during runtime_suspend/resume.
> After that, it stopped detecting the port status change event when a device was plugged
> to an external HUB. The wakeup irq was coming and the root hub/controller were being resumed,
> but after that, no hub_irq.
Wait a minute. I'm not clear on what happened. You're starting out
with the controller, the root hub, and the external hub all suspended,
right? Then you plugged a new device into the external hub. This
caused the controller and the root hub to wake up, but not the external
hub?
> Adding some delay (or printk) somewhere in the resume path fixes the issue. I'm not sure what
> is going on and why the delay is needed. Below is the ehci-omap patch. I've put the delay
> in the runtime_resume handler.
>
> e.g. log
>
> [ 8.674377] usb usb1: usb wakeup-resume
> [ 8.678833] ehci-omap 48064800.ehci: omap_ehci_runtime_resume
> [ 8.695190] usb usb1: usb auto-resume
> [ 8.699066] ehci-omap 48064800.ehci: resume root hub
> [ 8.704437] hub 1-0:1.0: hub_resume
> [ 8.708312] hub 1-0:1.0: port 2: status 0507 change 0000
> [ 8.714630] hub 1-0:1.0: state 7 ports 3 chg 0000 evt 0000
>
> <---- gets stuck here in the failing case---->
>
> [ 8.723541] hub 1-0:1.0: state 7 ports 3 chg 0000 evt 0004
> [ 8.729400] ehci-omap 48064800.ehci: GetStatus port:2 status 001005 0 ACK POWER sig=se0 PE CONNECT
> [ 8.753204] usb 1-2: usb wakeup-resume
> [ 8.757293] usb 1-2: finish resume
> [ 8.761627] hub 1-2:1.0: hub_resume
Yeah, we need more debugging info. In ehci_irq(), right after the
"pstatus = ehci_readl(..." line, what is the value of pstatus? And in
the GetPortStatus case of ehci_hub_control(), right after the "temp =
ehci_readl(..." line, what is the value of temp?
> @@ -286,15 +293,70 @@ static const struct of_device_id omap_ehci_dt_ids[] = {
>
> MODULE_DEVICE_TABLE(of, omap_ehci_dt_ids);
>
> +static int omap_ehci_suspend(struct device *dev)
> +{
> + struct usb_hcd *hcd = dev_get_drvdata(dev);
> + bool do_wakeup = device_may_wakeup(dev);
> +
> + dev_dbg(dev, "%s: do_wakeup: %d\n", __func__, do_wakeup);
> +
> + return ehci_suspend(hcd, do_wakeup);
> +}
> +
> +static int omap_ehci_resume(struct device *dev)
> +{
> + struct usb_hcd *hcd = dev_get_drvdata(dev);
> +
> + dev_dbg(dev, "%s\n", __func__);
> +
> + return ehci_resume(hcd, false);
> +}
Those two routines look okay.
> +static int omap_ehci_runtime_suspend(struct device *dev)
> +{
> + struct usb_hcd *hcd = dev_get_drvdata(dev);
> + struct omap_hcd *omap = (struct omap_hcd *)hcd_to_ehci(hcd)->priv;
> + bool do_wakeup = device_may_wakeup(dev);
> +
> + dev_dbg(dev, "%s\n", __func__);
> +
> + if (omap->initialized)
> + ehci_suspend(hcd, do_wakeup);
Here you should not use do_wakeup. The second argument should always
be "true", because wakeup is always enabled during runtime suspend.
Also, why do you need omap->initialized? Do you think you might get a
wakeup interrupt before the controller has been fully set up? I don't
see how you could, given the pm_runtime_get_sync() call in the probe
routine.
Alan Stern
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