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

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Hi Brian,

On 08/19/2017 01:01 AM, Brian Norris wrote:
Did you test that this works out correctly as a level-triggered
interrupt? IIUC, the dummy handler won't mask the interrupt, so it might
keep firing. See:

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.

hmmm, right, but as i replied at cros partner issue, this irq handle might not be called actually...

in my test on cros 4.4 kernel, it would break by irq_may_run(returning false):
static bool irq_may_run(struct irq_desc *desc)
{
...
        /*
         * If the interrupt is an armed wakeup source, mark it pending
         * and suspended, disable it and notify the pm core about the
         * event.
         */
        if (irq_pm_check_wakeup(desc))
                return false;


bool irq_pm_check_wakeup(struct irq_desc *desc)
{
        if (irqd_is_wakeup_armed(&desc->irq_data)) {
                irqd_clear(&desc->irq_data, IRQD_WAKEUP_ARMED);
                desc->istate |= IRQS_SUSPENDED | IRQS_PENDING;
                desc->depth++;
                irq_disable(desc); <--- disabled here
                pm_system_irq_wakeup(irq_desc_get_irq(desc));
                return true;



and for irqd_is_wakeup_armed:

static bool suspend_device_irq(struct irq_desc *desc)
{
...
        if (irqd_is_wakeup_set(&desc->irq_data)) {
irqd_set(&desc->irq_data, IRQD_WAKEUP_ARMED); <-- set irqd_is_wakeup_armed here


void dpm_noirq_begin(void)
{
        cpuidle_pause();
        device_wakeup_arm_wake_irqs();
        suspend_device_irqs();


so unless we get an irq between device_wakeup_arm_wake_irqs and suspend_device_irq, the irq_pm_check_wakeup would not let us get to handle_threaded_wake_irq...



BTW, in another context, Tony suggested we might need to fix up the IRQ flags
like this:

int dev_pm_set_dedicated_wake_irq(struct device *dev, int irq)
{
...
         err = request_threaded_irq(irq, NULL, handle_threaded_wake_irq,
-                                  IRQF_ONESHOT, dev_name(dev), wirq);
+                                  IRQF_ONESHOT | irq_get_trigger_type(irq), dev_name(dev), wirq);

But IIUC, that's not actually necessary, because __setup_irq()
automatically configures the trigger type if the driver didn't request
one explicitly.

actually this would not work...irq_get_trigger_type would return zero due to a bug which we have a patch for it already:

9908207 New [tip:irq/urgent] genirq: Restore trigger settings in irq_modify_status()


BTW, using dev_name for the name of this wake irq seems not very convenient...maybe add a ":wake" suffix?

Brian





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