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

[Tony Lindgren <tony@atomide.com>]

* Brian Norris <briannorris@chromium.org> [170818 10:01]:
> + Tony
> 
> On Thu, Aug 17, 2017 at 08:04:29PM +0800, Jeffy Chen wrote:
> > Add support for PCIE_WAKE pin in rockchip pcie driver.
> > 
> > Signed-off-by: Jeffy Chen <jeffy.chen@rock-chips.com>
> > ---
> > 
> > Changes in v2:
> > Use dev_pm_set_dedicated_wake_irq
> >         -- Suggested by Brian Norris <briannorris@chromium.com>
> > 
> >  drivers/pci/host/pcie-rockchip.c | 13 ++++++++++++-
> >  1 file changed, 12 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/pci/host/pcie-rockchip.c b/drivers/pci/host/pcie-rockchip.c
> > index 7bb9870f6d8c..c2b973c738fe 100644
> > --- a/drivers/pci/host/pcie-rockchip.c
> > +++ b/drivers/pci/host/pcie-rockchip.c
> > @@ -36,6 +36,7 @@
> >  #include <linux/pci_ids.h>
> >  #include <linux/phy/phy.h>
> >  #include <linux/platform_device.h>
> > +#include <linux/pm_wakeirq.h>
> >  #include <linux/reset.h>
> >  #include <linux/regmap.h>
> >  
> > @@ -853,7 +854,6 @@ static void rockchip_pcie_legacy_int_handler(struct irq_desc *desc)
> >  	chained_irq_exit(chip, desc);
> >  }
> >  
> > -
> >  /**
> >   * rockchip_pcie_parse_dt - Parse Device Tree
> >   * @rockchip: PCIe port information
> > @@ -1018,6 +1018,14 @@ static int rockchip_pcie_parse_dt(struct rockchip_pcie *rockchip)
> >  		return err;
> >  	}
> >  
> > +	device_init_wakeup(dev, true);
> > +	irq = platform_get_irq_byname(pdev, "wake");
> > +	if (irq >= 0) {
> > +		err = dev_pm_set_dedicated_wake_irq(dev, irq);
> 
> 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.

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.

> 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.

OK so we should make sure that the triggering is parsed
properly when passed in from device tree.

Regards,

Tony

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