linux-kernel - Re: [PATCH 1/3] clocksource: atmel-st: Remove irq handler when clock event is unused

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Message-ID: <20150718222308.GA30489@piout.net>
Date:	Sun, 19 Jul 2015 00:23:08 +0200
From:	Alexandre Belloni <alexandre.belloni@...e-electrons.com>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Nicolas Ferre <nicolas.ferre@...el.com>,
	Boris Brezillon <boris.brezillon@...e-electrons.com>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	David Dueck <davidcdueck@...glemail.com>
Subject: Re: [PATCH 1/3] clocksource: atmel-st: Remove irq handler when clock
 event is unused

On 18/07/2015 at 10:12:03 +0200, Thomas Gleixner wrote :
> On Fri, 17 Jul 2015, Alexandre Belloni wrote:
> > +static int atmel_st_request_irq(struct clock_event_device *dev)
> > +{
> > +	int ret;
> > +
> > +	if (clockevent_state_periodic(dev) || clockevent_state_oneshot(dev))
> > +		return 0;
> > +
> > +	ret = request_irq(irq, at91rm9200_timer_interrupt,
> > +			  IRQF_SHARED | IRQF_TIMER | IRQF_IRQPOLL,
> > +			  "at91_tick", regmap_st);
> > +	if (ret) {
> > +		pr_alert("Unable to setup IRQ\n");
> > +		return ret;
> > +	}
> > +
> >  	return 0;
> >  }
> >  
> >  static int clkevt32k_set_oneshot(struct clock_event_device *dev)
> >  {
> > +	int ret;
> > +
> >  	clkdev32k_disable_and_flush_irq();
> >  
> >  	/*
> >  	 * ALM for oneshot irqs, set by next_event()
> >  	 * before 32 seconds have passed.
> >  	 */
> > +	ret = atmel_st_request_irq(dev);
> 
> You cannot call request_irq() from interrupt disabled context. It
> works during early boot because might_sleep() is not active then, but
> if that happens during normal runtime it wont work.
> 

Indeed, clockevents_switch_state() has to be called with interrupts
disabled. So I'm not sure anymore how we should go about this change
(obviously, the same applies to the pit change). Do you have an idea?


-- 
Alexandre Belloni, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
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