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

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Message-ID: <CY1PR0301MB0843388CA3BB07493BC2907183610@CY1PR0301MB0843.namprd03.prod.outlook.com>
Date:	Tue, 25 Aug 2015 19:24:28 +0000
From:	Shenwei Wang <Shenwei.Wang@...escale.com>
To:	Sudeep Holla <sudeep.holla@....com>
CC:	"shawn.guo@...aro.org" <shawn.guo@...aro.org>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"jason@...edaemon.net" <jason@...edaemon.net>,
	"Huang Anson" <Anson.Huang@...escale.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: RE: [PATCH v9 1/1] irqchip: imx-gpcv2: IMX GPCv2 driver for wakeup
 sources



> -----Original Message-----
> From: Sudeep Holla [mailto:sudeep.holla@....com]
> Sent: 2015年8月25日 11:24
> To: Wang Shenwei-B38339
> Cc: Sudeep Holla; shawn.guo@...aro.org; tglx@...utronix.de;
> jason@...edaemon.net; Huang Yongcai-B20788; linux-kernel@...r.kernel.org;
> linux-arm-kernel@...ts.infradead.org
> 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
	 * IRQCHIP_MASK_ON_SUSPEND.
	 */
	if (irq_desc_get_chip(desc)->flags & IRQCHIP_MASK_ON_SUSPEND)
		mask_irq(desc);

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?

Regards,
Shenwei


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