linux-kernel - [PATCH 1/3] clocksource: atmel-st: Remove irq handler when clock event is unused

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Message-Id: <1437161608-26782-2-git-send-email-alexandre.belloni@free-electrons.com>
Date:	Fri, 17 Jul 2015 21:33:26 +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 1/3] clocksource: atmel-st: 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-st.c | 43 +++++++++++++++++++++++++++++-------
 1 file changed, 35 insertions(+), 8 deletions(-)

diff --git a/drivers/clocksource/timer-atmel-st.c b/drivers/clocksource/timer-atmel-st.c
index 41b7b6dc1d0d..a498b7446006 100644
--- a/drivers/clocksource/timer-atmel-st.c
+++ b/drivers/clocksource/timer-atmel-st.c
@@ -31,6 +31,7 @@
 
 static unsigned long last_crtr;
 static u32 irqmask;
+static int irq;
 static struct clock_event_device clkevt;
 static struct regmap *regmap_st;
 
@@ -121,17 +122,45 @@ static int clkevt32k_shutdown(struct clock_event_device *evt)
 	clkdev32k_disable_and_flush_irq();
 	irqmask = 0;
 	regmap_write(regmap_st, AT91_ST_IER, irqmask);
+
+	if (clockevent_state_periodic(evt) || clockevent_state_oneshot(evt))
+		free_irq(irq, regmap_st);
+
+	return 0;
+}
+
+static int atmel_st_request_irq(struct clock_event_device *dev)
+{
+	int ret;
+
+	if (clockevent_state_periodic(dev) || clockevent_state_oneshot(dev))
+		return 0;
+
+	ret = request_irq(irq, at91rm9200_timer_interrupt,
+			  IRQF_SHARED | IRQF_TIMER | IRQF_IRQPOLL,
+			  "at91_tick", regmap_st);
+	if (ret) {
+		pr_alert("Unable to setup IRQ\n");
+		return ret;
+	}
+
 	return 0;
 }
 
 static int clkevt32k_set_oneshot(struct clock_event_device *dev)
 {
+	int ret;
+
 	clkdev32k_disable_and_flush_irq();
 
 	/*
 	 * ALM for oneshot irqs, set by next_event()
 	 * before 32 seconds have passed.
 	 */
+	ret = atmel_st_request_irq(dev);
+	if (ret)
+		return ret;
+
 	irqmask = AT91_ST_ALMS;
 	regmap_write(regmap_st, AT91_ST_RTAR, last_crtr);
 	regmap_write(regmap_st, AT91_ST_IER, irqmask);
@@ -140,9 +169,15 @@ static int clkevt32k_set_oneshot(struct clock_event_device *dev)
 
 static int clkevt32k_set_periodic(struct clock_event_device *dev)
 {
+	int ret;
+
 	clkdev32k_disable_and_flush_irq();
 
 	/* PIT for periodic irqs; fixed rate of 1/HZ */
+	ret = atmel_st_request_irq(dev);
+	if (ret)
+		return ret;
+
 	irqmask = AT91_ST_PITS;
 	regmap_write(regmap_st, AT91_ST_PIMR, RM9200_TIMER_LATCH);
 	regmap_write(regmap_st, AT91_ST_IER, irqmask);
@@ -198,7 +233,6 @@ static struct clock_event_device clkevt = {
 static void __init atmel_st_timer_init(struct device_node *node)
 {
 	unsigned int val;
-	int irq, ret;
 
 	regmap_st = syscon_node_to_regmap(node);
 	if (IS_ERR(regmap_st))
@@ -214,13 +248,6 @@ static void __init atmel_st_timer_init(struct device_node *node)
 	if (!irq)
 		panic(pr_fmt("Unable to get IRQ from DT\n"));
 
-	/* Make IRQs happen for the system timer */
-	ret = request_irq(irq, at91rm9200_timer_interrupt,
-			  IRQF_SHARED | IRQF_TIMER | IRQF_IRQPOLL,
-			  "at91_tick", regmap_st);
-	if (ret)
-		panic(pr_fmt("Unable to setup IRQ\n"));
-
 	/* The 32KiHz "Slow Clock" (tick every 30517.58 nanoseconds) is used
 	 * directly for the clocksource and all clockevents, after adjusting
 	 * its prescaler from the 1 Hz default.
-- 
2.1.4

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