linux-kernel - Re: [PATCH] rtc: rtc-twl: ensure IRQ is wakeup enabled

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Message-Id: <20130603161303.55e9da049744656541e9048f@linux-foundation.org>
Date:	Mon, 3 Jun 2013 16:13:03 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Kevin Hilman <khilman@...aro.org>
Cc:	rtc-linux@...glegroups.com, linux-omap@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linaro-kernel@...ts.linaro.org,
	Alessandro Zummo <a.zummo@...ertech.it>,
	Tony Lindgren <tony@...mide.com>,
	linux-kernel@...r.kernel.org (open list)
Subject: Re: [PATCH] rtc: rtc-twl: ensure IRQ is wakeup enabled

On Fri, 31 May 2013 15:37:07 -0700 Kevin Hilman <khilman@...aro.org> wrote:

> Currently, the RTC IRQ is never wakeup-enabled so is not capable of
> bringing the system out of suspend.
> 
> On OMAP platforms, we have gotten by without this because the TWL RTC
> is on an I2C-connected chip which is capable of waking up the OMAP via
> the IO ring when the OMAP is in low-power states.
> 
> However, if the OMAP suspends without hitting the low-power states
> (and the IO ring is not enabled), RTC wakeups will not work because
> the IRQ is not wakeup enabled.
> 
> To fix, ensure the RTC IRQ is wakeup enabled whenever the RTC alarm is
> set.
> 
> --- a/drivers/rtc/rtc-twl.c
> +++ b/drivers/rtc/rtc-twl.c
> @@ -213,12 +213,24 @@ static int mask_rtc_irq_bit(unsigned char bit)
>  
>  static int twl_rtc_alarm_irq_enable(struct device *dev, unsigned enabled)
>  {
> +	struct platform_device *pdev = to_platform_device(dev);
> +	int irq = platform_get_irq(pdev, 0);
> +	static bool twl_rtc_wake_enabled;
>  	int ret;
>  
> -	if (enabled)
> +	if (enabled) {
>  		ret = set_rtc_irq_bit(BIT_RTC_INTERRUPTS_REG_IT_ALARM_M);
> -	else
> +		if (device_can_wakeup(dev) && !twl_rtc_wake_enabled) {
> +			enable_irq_wake(irq);
> +			twl_rtc_wake_enabled = true;
> +		}
> +	} else {
>  		ret = mask_rtc_irq_bit(BIT_RTC_INTERRUPTS_REG_IT_ALARM_M);
> +		if (twl_rtc_wake_enabled) {
> +			disable_irq_wake(irq);
> +			twl_rtc_wake_enabled = false;
> +		}
> +	}

Why do we need this (slightly racy) logic with twl_rtc_wake_enabled? 
Other drivers don't do this.

Should we test device_may_wakeup() befre running disable_irq_wake()? 
Most drivers seem to do this, but it's all a bit foggy.

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