linux-kernel - [PATCH] Optimize i8259 code a bit.

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Date:	Sun, 28 Oct 2007 23:11:45 +0000
From:	Ralf Baechle <ralf@...ux-mips.org>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>
Cc:	linux-kernel@...r.kernel.org
Subject: [PATCH] Optimize i8259 code a bit.

The timer code always calls the clock_event_device set_net_event and
set_mode methods with interrupts disabled, so no need to use
spin_lock_irqsave / spin_unlock_irqrestore for those.

 arch/mips/kernel/i8253.c |   12 ++++--------
 arch/x86/kernel/i8253.c  |   12 ++++--------
 2 files changed, 8 insertions(+), 16 deletions(-)

diff --git a/arch/mips/kernel/i8253.c b/arch/mips/kernel/i8253.c
index 5d9830d..1b54674 100644
--- a/arch/mips/kernel/i8253.c
+++ b/arch/mips/kernel/i8253.c
@@ -23,9 +23,7 @@ static DEFINE_SPINLOCK(i8253_lock);
 static void init_pit_timer(enum clock_event_mode mode,
 			   struct clock_event_device *evt)
 {
-	unsigned long flags;
-
-	spin_lock_irqsave(&i8253_lock, flags);
+	spin_lock(&i8253_lock);
 
 	switch(mode) {
 	case CLOCK_EVT_MODE_PERIODIC:
@@ -54,7 +52,7 @@ static void init_pit_timer(enum clock_event_mode mode,
 		/* Nothing to do here */
 		break;
 	}
-	spin_unlock_irqrestore(&i8253_lock, flags);
+	spin_unlock(&i8253_lock);
 }
 
 /*
@@ -64,12 +62,10 @@ static void init_pit_timer(enum clock_event_mode mode,
  */
 static int pit_next_event(unsigned long delta, struct clock_event_device *evt)
 {
-	unsigned long flags;
-
-	spin_lock_irqsave(&i8253_lock, flags);
+	spin_lock(&i8253_lock);
 	outb_p(delta & 0xff , PIT_CH0);	/* LSB */
 	outb(delta >> 8 , PIT_CH0);	/* MSB */
-	spin_unlock_irqrestore(&i8253_lock, flags);
+	spin_unlock(&i8253_lock);
 
 	return 0;
 }
diff --git a/arch/x86/kernel/i8253.c b/arch/x86/kernel/i8253.c
index a42c807..5246515 100644
--- a/arch/x86/kernel/i8253.c
+++ b/arch/x86/kernel/i8253.c
@@ -31,9 +31,7 @@ struct clock_event_device *global_clock_event;
 static void init_pit_timer(enum clock_event_mode mode,
 			   struct clock_event_device *evt)
 {
-	unsigned long flags;
-
-	spin_lock_irqsave(&i8253_lock, flags);
+	spin_lock(&i8253_lock);
 
 	switch(mode) {
 	case CLOCK_EVT_MODE_PERIODIC:
@@ -62,7 +60,7 @@ static void init_pit_timer(enum clock_event_mode mode,
 		/* Nothing to do here */
 		break;
 	}
-	spin_unlock_irqrestore(&i8253_lock, flags);
+	spin_unlock(&i8253_lock);
 }
 
 /*
@@ -72,12 +70,10 @@ static void init_pit_timer(enum clock_event_mode mode,
  */
 static int pit_next_event(unsigned long delta, struct clock_event_device *evt)
 {
-	unsigned long flags;
-
-	spin_lock_irqsave(&i8253_lock, flags);
+	spin_lock(&i8253_lock);
 	outb_p(delta & 0xff , PIT_CH0);	/* LSB */
 	outb(delta >> 8 , PIT_CH0);	/* MSB */
-	spin_unlock_irqrestore(&i8253_lock, flags);
+	spin_unlock(&i8253_lock);
 
 	return 0;
 }
-
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