linux-kernel - Re: [PATCH 0/3] rtc: pcf8563: Fix unhandled interrupt storm

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Date:   Mon, 24 Jun 2019 12:42:34 +0200
From:   Alexandre Belloni <alexandre.belloni@...tlin.com>
To:     Chen-Yu Tsai <wens@...nel.org>
Cc:     Maxime Ripard <maxime.ripard@...tlin.com>,
        Alessandro Zummo <a.zummo@...ertech.it>,
        Vincent Donnefort <vdonnefort@...il.com>,
        linux-rtc@...r.kernel.org, devicetree <devicetree@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/3] rtc: pcf8563: Fix unhandled interrupt storm

On 24/06/2019 18:34:29+0800, Chen-Yu Tsai wrote:
> On Fri, Jun 21, 2019 at 12:22 AM Alexandre Belloni
> <alexandre.belloni@...tlin.com> wrote:
> >
> > On 04/06/2019 12:23:34+0800, Chen-Yu Tsai wrote:
> > > From: Chen-Yu Tsai <wens@...e.org>
> > >
> > > Hi everyone,
> > >
> > > While bringing up my Pine H64, I encountered an interrupt storm from the
> > > pcf8563 RTC. The RTC chip's interrupt line is shared with the PMIC, and
> > > was not properly added to the device tree. Also, the driver was using an
> > > trigger method incompatible with the PMIC, preventing the interrupt line
> > > from being shared. Last, the driver only clears and masks the alarm
> > > interrupt, while leaving the timer interrupt untouched. This is a
> > > problem if previous systems left the timer interrupt enabled, and there
> > > was an interrupt pending.
> > >
> > > This patch set fixes all three issues, one per patch.
> > >
> > > Please have a look.
> > >
> >
> > I don't have that particular RTC so I can't test but the interrupt
> > handling in pcf8563_irq seems problematic too. I guess the RTC will only
> > trigger once per second because the call to pcf8563_set_alarm_mode will
> > explicitely leave the alarm enabled. The core doesn't really care but it
> > doesn't really expect the alarm to stay enabled. i.e. It will ensure the
> > alarm is enabled again after setting it when necessary. I think it would
> > be safer to simply clear both AIE and AF here. Could you test?
> 
> Yeah, that bit looked weird to me as well. And actually the alarm doesn't
> go down to the second, only the minute.
> 
> Is there a test program I can use to test the alarms?
> 

Sure, tools/testing/selftests/rtc/rtctest.c if you use a recent enough
version, it will test minute boundaries.


-- 
Alexandre Belloni, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com