linux-kernel - [PATCH] clockevents/drivers/mtk: Fix spurious interrupt leading to crash

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Date:	Mon, 24 Aug 2015 15:30:44 +0200
From:	Daniel Lezcano <daniel.lezcano@...aro.org>
To:	yingjoe.chen@...iatek.com
Cc:	djkurtz@...omium.org, sboyd@...eaurora.org, tglx@...utronix.de,
	jamesjj.liao@...iatek.com, linux@....linux.org.uk,
	srv_heupstream@...iatek.com, arnd@...db.de,
	catalin.marinas@....com, kernel@...gutronix.de,
	matthias.bgg@...il.com,
	linux-kernel@...r.kernel.org (open list:CLOCKSOURCE, CLOC...),
	linux-arm-kernel@...ts.infradead.org (moderated list:ARM/Mediatek
	SoC...),
	linux-mediatek@...ts.infradead.org (moderated list:ARM/Mediatek SoC...)
Subject: [PATCH] clockevents/drivers/mtk: Fix spurious interrupt leading to crash

After analysis done by Yingjoe Chen, the timer appears to have a pending
interrupt when it is enabled.

Fix this by acknowledging the pending interrupt when enabling the timer
interrupt.

Signed-off-by: Daniel Lezcano <daniel.lezcano@...aro.org>
---
 drivers/clocksource/mtk_timer.c | 13 +++----------
 1 file changed, 3 insertions(+), 10 deletions(-)

diff --git a/drivers/clocksource/mtk_timer.c b/drivers/clocksource/mtk_timer.c
index 4cd16fb..13543a8 100644
--- a/drivers/clocksource/mtk_timer.c
+++ b/drivers/clocksource/mtk_timer.c
@@ -156,14 +156,6 @@ static irqreturn_t mtk_timer_interrupt(int irq, void *dev_id)
 	return IRQ_HANDLED;
 }
 
-static void mtk_timer_global_reset(struct mtk_clock_event_device *evt)
-{
-	/* Disable all interrupts */
-	writel(0x0, evt->gpt_base + GPT_IRQ_EN_REG);
-	/* Acknowledge all interrupts */
-	writel(0x3f, evt->gpt_base + GPT_IRQ_ACK_REG);
-}
-
 static void
 mtk_timer_setup(struct mtk_clock_event_device *evt, u8 timer, u8 option)
 {
@@ -183,6 +175,9 @@ static void mtk_timer_enable_irq(struct mtk_clock_event_device *evt, u8 timer)
 {
 	u32 val;
 
+        /* Acknowledge all spurious pending interrupts */
+        writel(0x3f, 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);
@@ -232,8 +227,6 @@ static void __init mtk_timer_init(struct device_node *node)
 	}
 	rate = clk_get_rate(clk);
 
-	mtk_timer_global_reset(evt);
-
 	if (request_irq(evt->dev.irq, mtk_timer_interrupt,
 			IRQF_TIMER | IRQF_IRQPOLL, "mtk_timer", evt)) {
 		pr_warn("failed to setup irq %d\n", evt->dev.irq);
-- 
1.9.1

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