linux-kernel - [PATCH 3/3] clocksource: atmel-pit: Remove irq handler when clock event is unused

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Date:	Fri, 17 Jul 2015 21:33:28 +0200
From:	Alexandre Belloni <alexandre.belloni@...e-electrons.com>
To:	Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Nicolas Ferre <nicolas.ferre@...el.com>,
	Boris Brezillon <boris.brezillon@...e-electrons.com>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	David Dueck <davidcdueck@...glemail.com>,
	Alexandre Belloni <alexandre.belloni@...e-electrons.com>
Subject: [PATCH 3/3] clocksource: atmel-pit: Remove irq handler when clock event is unused

Setup and remove the interrupt handler in clock event mode selection.
This avoids calling the (shared) interrupt handler when the device is not
used.

Signed-off-by: Alexandre Belloni <alexandre.belloni@...e-electrons.com>
---
 drivers/clocksource/timer-atmel-pit.c | 86 +++++++++++++++++++----------------
 1 file changed, 46 insertions(+), 40 deletions(-)

diff --git a/drivers/clocksource/timer-atmel-pit.c b/drivers/clocksource/timer-atmel-pit.c
index e64af62a186c..c77aafa7846e 100644
--- a/drivers/clocksource/timer-atmel-pit.c
+++ b/drivers/clocksource/timer-atmel-pit.c
@@ -96,15 +96,61 @@ static int pit_clkevt_shutdown(struct clock_event_device *dev)
 
 	/* disable irq, leaving the clocksource active */
 	pit_write(data->base, AT91_PIT_MR, (data->cycle - 1) | AT91_PIT_PITEN);
+
+	if (clockevent_state_periodic(dev))
+		free_irq(data->irq, data);
+
 	return 0;
 }
 
 /*
+ * IRQ handler for the timer.
+ */
+static irqreturn_t at91sam926x_pit_interrupt(int irq, void *dev_id)
+{
+	struct pit_data *data = dev_id;
+
+	/*
+	 * irqs should be disabled here, but as the irq is shared they are only
+	 * guaranteed to be off if the timer irq is registered first.
+	 */
+	WARN_ON_ONCE(!irqs_disabled());
+
+	/* The PIT interrupt may be disabled, and is shared */
+	if (clockevent_state_periodic(&data->clkevt) &&
+	    (pit_read(data->base, AT91_PIT_SR) & AT91_PIT_PITS)) {
+		unsigned nr_ticks;
+
+		/* Get number of ticks performed before irq, and ack it */
+		nr_ticks = PIT_PICNT(pit_read(data->base, AT91_PIT_PIVR));
+		do {
+			data->cnt += data->cycle;
+			data->clkevt.event_handler(&data->clkevt);
+			nr_ticks--;
+		} while (nr_ticks);
+
+		return IRQ_HANDLED;
+	}
+
+	return IRQ_NONE;
+}
+
+/*
  * Clockevent device:  interrupts every 1/HZ (== pit_cycles * MCK/16)
  */
 static int pit_clkevt_set_periodic(struct clock_event_device *dev)
 {
 	struct pit_data *data = clkevt_to_pit_data(dev);
+	int		ret;
+
+	/* Set up irq handler */
+	ret = request_irq(data->irq, at91sam926x_pit_interrupt,
+			  IRQF_SHARED | IRQF_TIMER | IRQF_IRQPOLL,
+			  "at91_tick", data);
+	if (ret) {
+		pr_alert("Unable to setup IRQ\n");
+		return ret;
+	}
 
 	/* update clocksource counter */
 	data->cnt += data->cycle * PIT_PICNT(pit_read(data->base, AT91_PIT_PIVR));
@@ -143,38 +189,6 @@ static void at91sam926x_pit_resume(struct clock_event_device *cedev)
 }
 
 /*
- * IRQ handler for the timer.
- */
-static irqreturn_t at91sam926x_pit_interrupt(int irq, void *dev_id)
-{
-	struct pit_data *data = dev_id;
-
-	/*
-	 * irqs should be disabled here, but as the irq is shared they are only
-	 * guaranteed to be off if the timer irq is registered first.
-	 */
-	WARN_ON_ONCE(!irqs_disabled());
-
-	/* The PIT interrupt may be disabled, and is shared */
-	if (clockevent_state_periodic(&data->clkevt) &&
-	    (pit_read(data->base, AT91_PIT_SR) & AT91_PIT_PITS)) {
-		unsigned nr_ticks;
-
-		/* Get number of ticks performed before irq, and ack it */
-		nr_ticks = PIT_PICNT(pit_read(data->base, AT91_PIT_PIVR));
-		do {
-			data->cnt += data->cycle;
-			data->clkevt.event_handler(&data->clkevt);
-			nr_ticks--;
-		} while (nr_ticks);
-
-		return IRQ_HANDLED;
-	}
-
-	return IRQ_NONE;
-}
-
-/*
  * Set up both clocksource and clockevent support.
  */
 static void __init at91sam926x_pit_dt_init(struct device_node *node)
@@ -182,7 +196,6 @@ static void __init at91sam926x_pit_dt_init(struct device_node *node)
 	struct pit_data *data;
 	unsigned long	pit_rate;
 	unsigned	bits;
-	int		ret;
 
 	data = kzalloc(sizeof(*data), GFP_KERNEL);
 	if (!data)
@@ -228,13 +241,6 @@ static void __init at91sam926x_pit_dt_init(struct device_node *node)
 	data->clksrc.flags = CLOCK_SOURCE_IS_CONTINUOUS,
 	clocksource_register_hz(&data->clksrc, pit_rate);
 
-	/* Set up irq handler */
-	ret = request_irq(data->irq, at91sam926x_pit_interrupt,
-			  IRQF_SHARED | IRQF_TIMER | IRQF_IRQPOLL,
-			  "at91_tick", data);
-	if (ret)
-		panic(pr_fmt("Unable to setup IRQ\n"));
-
 	/* Set up and register clockevents */
 	data->clkevt.name = "pit";
 	data->clkevt.features = CLOCK_EVT_FEAT_PERIODIC;
-- 
2.1.4

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