linux-kernel - Re: [PATCH 1/7] clocksource: mediatek: Don't run event

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Date:	Mon, 4 May 2015 23:13:59 +0800
From:	Yingjoe Chen <yingjoe.chen@...iatek.com>
To:	Daniel Lezcano <daniel.lezcano@...aro.org>
CC:	Matthias Brugger <matthias.bgg@...il.com>,
	Mark Rutland <mark.rutland@....com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Arnd Bergmann <arnd@...db.de>, Olof Johansson <olof@...om.net>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Russell King <linux@....linux.org.uk>,
	Jason Cooper <jason@...edaemon.net>,
	Catalin Marinas <catalin.marinas@....com>,
	Marc Carino <marc.ceeeee@...il.com>,
	"Lorenzo Pieralisi" <lorenzo.pieralisi@....com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-mediatek@...ts.infradead.org>,
	srv_heupstream <srv_heupstream@...iatek.com>,
	Sascha Hauer <kernel@...gutronix.de>
Subject: Re: [PATCH 1/7] clocksource: mediatek: Don't run event_handler if
 it is NULL

On Mon, 2015-05-04 at 10:44 +0200, Daniel Lezcano wrote:
> On 05/04/2015 10:34 AM, Matthias Brugger wrote:
> > 2015-05-04 10:14 GMT+02:00 Daniel Lezcano <daniel.lezcano@...aro.org>:
> >> On 05/01/2015 09:43 AM, Yingjoe Chen wrote:
> >>>
> >>> Spurious timer interrupt is noticed in mtk timer and cause kernel
> >>> crash. In mtk_timer_interrupt(), only run event_handler if it is
> >>> not NULL.
> >>>
> >>> Signed-off-by: Yingjoe Chen <yingjoe.chen@...iatek.com>
> >>> ---
> >>>    drivers/clocksource/mtk_timer.c | 3 ++-
> >>>    1 file changed, 2 insertions(+), 1 deletion(-)
> >>>
> >>> diff --git a/drivers/clocksource/mtk_timer.c
> >>> b/drivers/clocksource/mtk_timer.c
> >>> index 68ab423..85e0ab5 100644
> >>> --- a/drivers/clocksource/mtk_timer.c
> >>> +++ b/drivers/clocksource/mtk_timer.c
> >>> @@ -143,7 +143,8 @@ static irqreturn_t mtk_timer_interrupt(int irq, void
> >>> *dev_id)
> >>>
> >>>          /* Acknowledge timer0 irq */
> >>>          writel(GPT_IRQ_ACK(GPT_CLK_EVT), evt->gpt_base + GPT_IRQ_ACK_REG);
> >>> -       evt->dev.event_handler(&evt->dev);
> >>> +       if (evt->dev.event_handler)
> >>> +               evt->dev.event_handler(&evt->dev);
> >>>
> >>>          return IRQ_HANDLED;
> >>>    }
> >>>
> >>
> >> This fix does not look good.
> >>
> >> Could you try by requesting the irq *after* clockevents_config_and_register
> >> in the init sequence [1] ?
> >>
> >
> >  From my understanding [1] should already fix this.
> >
> > [1] https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/commit/drivers/clocksource/mtk_timer.c?id=d4a19eb3b15a4ba98f627182f48d5bc0cffae670
> 
> Indeed it seems to fix it. But I think request_irq should be done after 
> clockevents_config_and_register in any case.
> 
> Yingjoe, are the spurious interrupts occurring with the fix Matthias 
> mentions ?
> 

Hi Daniel, Matthias,

Thanks for your review.

Unfortunately, I still saw the spurious interrupts with both fixes.

After some experiments, it seems the HW will latch irq status even when 
IRQ is disabled. I can fix this issue by either ack irq before enable
irq(like patch below), or not enable clock event before enable irq.

I'll come up a fix base on this next time.

diff --git a/drivers/clocksource/mtk_timer.c
b/drivers/clocksource/mtk_timer.c
index 9a90c7b..c5f804a 100644
--- a/drivers/clocksource/mtk_timer.c
+++ b/drivers/clocksource/mtk_timer.c
@@ -184,6 +183,7 @@ static void mtk_timer_enable_irq(struct
mtk_clock_event_device *evt, u8 timer)
 {
 	u32 val;
 
+	writel(GPT_IRQ_ENABLE(timer), evt->gpt_base + GPT_IRQ_ACK_REG);
 	val = readl(evt->gpt_base + GPT_IRQ_EN_REG);
 	writel(val | GPT_IRQ_ENABLE(timer),
 			evt->gpt_base + GPT_IRQ_EN_REG);


Joe.C



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