From: Benedikt Spranger <b.spranger@linutronix.de>
Date: Sat, 6 Mar 2010 17:47:10 +0100
Subject: ARM: AT91: PIT: Remove irq handler when clock event is unused
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.6/older/patches-4.6.2-rt5.tar.xz

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: Benedikt Spranger <b.spranger@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
[bigeasy: redo the patch with NR_IRQS_LEGACY which is probably required since
commit 8fe82a55 ("ARM: at91: sparse irq support") which is included since v3.6.
Patch based on what Sami Pietikäinen <Sami.Pietikainen@wapice.com> suggested].
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 drivers/clocksource/timer-atmel-pit.c |   17 +++++++++--------
 drivers/clocksource/timer-atmel-st.c  |   32 ++++++++++++++++++++++----------
 2 files changed, 31 insertions(+), 18 deletions(-)

--- a/drivers/clocksource/timer-atmel-pit.c
+++ b/drivers/clocksource/timer-atmel-pit.c
@@ -96,15 +96,24 @@ static int pit_clkevt_shutdown(struct cl
 
 	/* disable irq, leaving the clocksource active */
 	pit_write(data->base, AT91_PIT_MR, (data->cycle - 1) | AT91_PIT_PITEN);
+	free_irq(data->irq, data);
 	return 0;
 }
 
+static irqreturn_t at91sam926x_pit_interrupt(int irq, void *dev_id);
 /*
  * 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;
+
+	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"));
 
 	/* update clocksource counter */
 	data->cnt += data->cycle * PIT_PICNT(pit_read(data->base, AT91_PIT_PIVR));
@@ -181,7 +190,6 @@ static void __init at91sam926x_pit_commo
 {
 	unsigned long	pit_rate;
 	unsigned	bits;
-	int		ret;
 
 	/*
 	 * Use our actual MCK to figure out how many MCK/16 ticks per
@@ -206,13 +214,6 @@ static void __init at91sam926x_pit_commo
 	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;
--- a/drivers/clocksource/timer-atmel-st.c
+++ b/drivers/clocksource/timer-atmel-st.c
@@ -115,18 +115,29 @@ static void clkdev32k_disable_and_flush_
 	last_crtr = read_CRTR();
 }
 
+static int atmel_st_irq;
+
 static int clkevt32k_shutdown(struct clock_event_device *evt)
 {
 	clkdev32k_disable_and_flush_irq();
 	irqmask = 0;
 	regmap_write(regmap_st, AT91_ST_IER, irqmask);
+	free_irq(atmel_st_irq, regmap_st);
 	return 0;
 }
 
 static int clkevt32k_set_oneshot(struct clock_event_device *dev)
 {
+	int ret;
+
 	clkdev32k_disable_and_flush_irq();
 
+	ret = request_irq(atmel_st_irq, at91rm9200_timer_interrupt,
+			  IRQF_SHARED | IRQF_TIMER | IRQF_IRQPOLL,
+			  "at91_tick", regmap_st);
+	if (ret)
+		panic(pr_fmt("Unable to setup IRQ\n"));
+
 	/*
 	 * ALM for oneshot irqs, set by next_event()
 	 * before 32 seconds have passed.
@@ -139,8 +150,16 @@ static int clkevt32k_set_oneshot(struct
 
 static int clkevt32k_set_periodic(struct clock_event_device *dev)
 {
+	int ret;
+
 	clkdev32k_disable_and_flush_irq();
 
+	ret = request_irq(atmel_st_irq, at91rm9200_timer_interrupt,
+			  IRQF_SHARED | IRQF_TIMER | IRQF_IRQPOLL,
+			  "at91_tick", regmap_st);
+	if (ret)
+		panic(pr_fmt("Unable to setup IRQ\n"));
+
 	/* PIT for periodic irqs; fixed rate of 1/HZ */
 	irqmask = AT91_ST_PITS;
 	regmap_write(regmap_st, AT91_ST_PIMR, timer_latch);
@@ -198,7 +217,7 @@ static void __init atmel_st_timer_init(s
 {
 	struct clk *sclk;
 	unsigned int sclk_rate, val;
-	int irq, ret;
+	int ret;
 
 	regmap_st = syscon_node_to_regmap(node);
 	if (IS_ERR(regmap_st))
@@ -210,17 +229,10 @@ static void __init atmel_st_timer_init(s
 	regmap_read(regmap_st, AT91_ST_SR, &val);
 
 	/* Get the interrupts property */
-	irq  = irq_of_parse_and_map(node, 0);
-	if (!irq)
+	atmel_st_irq  = irq_of_parse_and_map(node, 0);
+	if (!atmel_st_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"));
-
 	sclk = of_clk_get(node, 0);
 	if (IS_ERR(sclk))
 		panic(pr_fmt("Unable to get slow clock\n"));
