linux-kernel - Re: [PATCH V1] rtc: da9063: access ordering error during RTC interrupt system power on

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Date:	Mon, 21 Dec 2015 09:19:08 +0100
From:	Alexandre Belloni <alexandre.belloni@...e-electrons.com>
To:	Steve Twiss <stwiss.opensource@...semi.com>
Cc:	Alessandro Zummo <a.zummo@...ertech.it>,
	LINUXKERNEL <linux-kernel@...r.kernel.org>,
	RTC-LINUX <rtc-linux@...glegroups.com>,
	David Dajun Chen <david.chen@...semi.com>,
	Support Opensource <support.opensource@...semi.com>
Subject: Re: [PATCH V1] rtc: da9063: access ordering error during RTC
 interrupt system power on

On 08/12/2015 at 16:28:39 +0000, Steve Twiss wrote :
> From: Steve Twiss <stwiss.opensource@...semi.com>
> 
> This fix alters the ordering of the IRQ and device registrations in the RTC
> driver probe function. This change will apply to the RTC driver that supports
> both DA9063 and DA9062 PMICs.
> 
> A problem could occur with the existing RTC driver if:
> 
> A system is started from a cold boot using the PMIC RTC IRQ to initiate a
> power on operation. For instance, if an RTC alarm is used to start a
> platform from power off.
> The existing driver IRQ is requested before the device has been properly
> registered.
> i.e.
>     ret = devm_request_threaded_irq() 
> comes before
>     rtc->rtc_dev = devm_rtc_device_register();
> 
> In this case, the interrupt can be called before the device has been
> registered and the handler can be called immediately. The IRQ handler
> da9063_alarm_event() contains the function call
> 
>     rtc_update_irq(rtc->rtc_dev, 1, RTC_IRQF | RTC_AF);
> 
> which in turn tries to access the unavailable rtc->rtc_dev.
> 
> The fix is to reorder the functions inside the RTC probe. The IRQ is
> requested after the RTC device resource has been registered so that
> get_irq_byname is the last thing to happen.
> 
> Signed-off-by: Steve Twiss <stwiss.opensource@...semi.com>

This patch has been applied and landed in v4.4-rc6


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