RE: [PATCH v9 1/1] irqchip: imx-gpcv2: IMX GPCv2 driver for wakeup sources

From: Shenwei Wang
Date: Tue Aug 25 2015 - 15:24:36 EST

> -----Original Message-----
> From: Sudeep Holla [mailto:sudeep.holla@xxxxxxx]
> Sent: 2015å8æ25æ 11:24
> To: Wang Shenwei-B38339
> Cc: Sudeep Holla; shawn.guo@xxxxxxxxxx; tglx@xxxxxxxxxxxxx;
> jason@xxxxxxxxxxxxxx; Huang Yongcai-B20788; linux-kernel@xxxxxxxxxxxxxxx;
> linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
> Subject: Re: [PATCH v9 1/1] irqchip: imx-gpcv2: IMX GPCv2 driver for wakeup
> >
> > You don't really understand what happens after a driver calls
> > enable_irq_wake. In suspend state, even the interrupt controller
> > itself is powered off. How can you get the system up again by just
> > using a SKIP_SET_WAKE.
> >
> Sorry for that, let me try to understand aloud. So you have irq_{un,}mask function
> that are called when interrupts are enabled and disabled. So suppose you have 3
> irqs that are enabled and only one of then is set as wakeup source.
> Now you call enable_irq_wake, you save that in wakeup_sources, fine.
> Later when you enter suspend, you save all the 3 active irqs in saved_irq_mask
> and over-write cpu2wakeup with wakeup_sources, right?
> All fine, what I am saying is let irq-core know that you want to mask the 2
> non-wakeup irqs you have using MASK_ON_SUSPEND. So when
> suspend_device_irqs is called in suspend path, that's done for you automatically
> and the cpu2wakeup will have just 1 wakeup enabled which is what you are doing
> in suspend callback, right ?

* Hardware which has no wakeup source configuration facility
* requires that the non wakeup interrupts are masked at the
* chip level. The chip implementation indicates that with
if (irq_desc_get_chip(desc)->flags & IRQCHIP_MASK_ON_SUSPEND)

IRQCHIP_MASK_ON_SUSPEND flag is for the hardware that has no wakeup source capability.
This GPCv2 block is designed to manage the wakeup source, so the flag does not make any sense.

> Now that it's already done for you, you need not do anything extra and hence just
> set SKIP_SET_WAKE to do nothing.

static int set_irq_wake_real(unsigned int irq, unsigned int on)
struct irq_desc *desc = irq_to_desc(irq);
int ret = -ENXIO;

if (irq_desc_get_chip(desc)->flags & IRQCHIP_SKIP_SET_WAKE)
return 0;

if (desc->irq_data.chip->irq_set_wake)
ret = desc->irq_data.chip->irq_set_wake(&desc->irq_data, on);

return ret;
From the codes above, if a irqchip can not handle the wakeup sources, it can set SKIP flag.
This driver is intended to manage the wakeup sources, what's the reason to skip here?


> Hope this clarifies, sorry if I am still missing to understand something here, but I
> don't see anything. Let me know.
> Regards,
> Sudeep