Re: [RFC PATCH v2 1/3] PCI: rockchip: Add support for pcie wake irq

[Tony Lindgren <tony@atomide.com>]

* jeffy <jeffy.chen@rock-chips.com> [170818 13:05]:
> Hi guys,
> 
> On 08/19/2017 02:14 AM, Tony Lindgren wrote:
> > > static irqreturn_t handle_threaded_wake_irq(int irq, void *_wirq)
> > > >{
> > > >         struct wake_irq *wirq = _wirq;
> > > >         int res;
> > > >
> > > >         /* Maybe abort suspend? */
> > > >         if (irqd_is_wakeup_set(irq_get_irq_data(irq))) {
> > > >                 pm_wakeup_event(wirq->dev, 0);
> > > >
> > > >                 return IRQ_HANDLED; <--- We can return here, with the trigger still asserted
> > > >         }
> > > >...
> > > >
> > > >This could cause some kind of an IRQ storm, including a lockup or
> > > >significant slowdown, I think.
> > Hmm yeah that should be checked. The test cases I have are all
> > edge interrupts where there is no status whatsoever after the
> > wake-up event except which irq fired.
> > 
> > To me it seems that the wakeirq consumer driver should be able
> > to clear the level wakeirq in it's runtime_resume, or even better,
> > maybe all it takes is just let the consumer driver's irq handler
> > clear the level wakeirq when it runs after runtime_resume.
> > 
> 
> i did some tests about it:
> [   70.335883] device_wakeup_arm_wake_irqs <-- enable wake irq
> [   70.335932] handle_threaded_wake_irq
> ...<--- a lot of wake irq handler log
> [   70.335965] suspend_device_irq
> [   70.335987] irq_pm_check_wakeup <--- wake and disable wake irq
> ...<--- no wake irq handler log
> [   70.336173] resume_irqs <-- enable wake irq
> [   70.336480] handle_threaded_wake_irq
> ...<--- a lot of wake irq handler log
> [   70.336600] device_wakeup_disarm_wake_irqs < disable wake irq
> ...<--- no wake irq handler log
> 
> 
> so it would indeed possible to get irq storm in device_wakeup_arm_wake_irqs
> to suspend_device_irq
> and resume_irqs to device_wakeup_disarm_wake_irqs.
> 
> 
> a simple workaround would be:
> enable_irq_wake
> suspend_device_irq
> enable_irq
> ...irq fired, irq_pm_check_wakeup disabled irq
> disable_irq
> resume_irqs
> disable_irq_wake
> 
> 
> 
> 
> and i have a hacky patch for that, which works well:
> 
> +++ b/drivers/pci/host/pcie-rockchip.c
> @@ -1308,6 +1308,8 @@ static int __maybe_unused
> rockchip_pcie_suspend_noirq(struct
> device *dev)
>         if (!IS_ERR(rockchip->vpcie0v9))
>                 regulator_disable(rockchip->vpcie0v9);
> 
> +       dev_pm_enable_wake_irq(dev);
> +
>         return ret;
>  }
> 
> @@ -1316,6 +1318,8 @@ static int __maybe_unused
> rockchip_pcie_resume_noirq(struct d
> evice *dev)
>         struct rockchip_pcie *rockchip = dev_get_drvdata(dev);
>         int err;
> 
> +       dev_pm_disable_wake_irq(dev);
> +
> 
> 
> @ -323,7 +324,7 @@ void dev_pm_arm_wake_irq(struct wake_irq *wirq)
>                 return;
> 
>         if (device_may_wakeup(wirq->dev)) {
> -               if (wirq->status & WAKE_IRQ_DEDICATED_ALLOCATED)
> +               if (0 && wirq->status & WAKE_IRQ_DEDICATED_ALLOCATED)
>                         enable_irq(wirq->irq);
> 
>                 enable_irq_wake(wirq->irq);
> @@ -345,7 +346,7 @@ void dev_pm_disarm_wake_irq(struct wake_irq *wirq)
>         if (device_may_wakeup(wirq->dev)) {
>                 disable_irq_wake(wirq->irq);
> 
> -               if (wirq->status & WAKE_IRQ_DEDICATED_ALLOCATED)
> +               if (0 && wirq->status & WAKE_IRQ_DEDICATED_ALLOCATED)
>                         disable_irq_nosync(wirq->irq);
>         }
> 
> 
> 
> which is basically move enable_irq and disable_irq to driver noirq stages,
> to avoid:
> 1/ not disabled by irq_pm_check_wakeup when it first fired
> 2/ re-enabled by resume_irq when it disabled by irq_pm_check_wakeup
> 
> 
> with that hack, i no longer saw the irq storm, and the irq handler would
> never be called:
> 
> [    9.693385] device_wakeup_arm_wake_irqs
> [    9.697130] suspend_device_irq
> <--- suspend noirq, enable wake irq
> [    9.716569] irq_pm_check_wakeup disable the wake irq
> <--- resume noirq, disable wake irq
> [    9.968115] resume_irqs <-- enable wake irq(not actually enable, since
> disabled twice)
> [   10.193072] device_wakeup_disarm_wake_irqs

OK, let's fix any wakeriq ordering issues to make it more
usable. Sounds like in your case the wakeirq needs to be enabled
late and disabled early, while in my test cases I can keep it
enabled basically any time.

If this is for suspend/resume, You could just register the
wakeirq on suspend and then remove it on resume. We do have at
least network drivers doing device_init_wakeup(dev, true) and
device_init_wakeup(dev, false) as needed for WOL, see for example
bfin_mac_ethtool_setwol().

Regards,

Tony


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