[RFC patch 24/32] x86: Simplify timer_ack magic in time_32.c

Thomas Gleixner
2009-08-21T21:35:23Z

[-- Attachment #1: x86-simplify-timer-ack-hack.patch --]
[-- Type: text/plain, Size: 2693 bytes --]

Let the compiler optimize the timer_ack magic away in the 32bit timer
interrupt and put the same code into time_64.c. It's optimized out for
CONFIG_X86_IO_APIC on 32bit and for 64bit because timer_ack is const 0
in both cases.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
arch/x86/include/asm/timer.h | 6 ++++--
arch/x86/kernel/time_32.c | 5 +++--
arch/x86/kernel/time_64.c | 14 ++++++++++++++
3 files changed, 21 insertions(+), 4 deletions(-)

Index: linux-2.6/arch/x86/include/asm/timer.h
===================================================================
--- linux-2.6.orig/arch/x86/include/asm/timer.h
+++ linux-2.6/arch/x86/include/asm/timer.h
@@ -9,11 +9,13 @@

unsigned long long native_sched_clock(void);
unsigned long native_calibrate_tsc(void);
+extern int recalibrate_cpu_khz(void);

-#ifdef CONFIG_X86_32
+#if defined(CONFIG_X86_32) && defined(CONFIG_X86_IO_APIC)
extern int timer_ack;
+#else
+# define timer_ack (0)
#endif
-extern int recalibrate_cpu_khz(void);

extern int no_timer_check;

Index: linux-2.6/arch/x86/kernel/time_32.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/time_32.c
+++ linux-2.6/arch/x86/kernel/time_32.c
@@ -22,7 +22,9 @@
#include <asm/time.h>
#include <asm/nmi.h>

+#if defined(CONFIG_X86_32) && defined(CONFIG_X86_IO_APIC)
int timer_ack;
+#endif

unsigned long profile_pc(struct pt_regs *regs)
{
@@ -59,7 +61,7 @@ static irqreturn_t timer_interrupt(int i
/* Keep nmi watchdog up to date */
inc_irq_stat(irq0_irqs);

-#ifdef CONFIG_X86_IO_APIC
+ /* Optimized out for !IO_APIC and x86_64 */
if (timer_ack) {
/*
* Subtle, when I/O APICs are used we have to ack timer IRQ
@@ -72,7 +74,6 @@ static irqreturn_t timer_interrupt(int i
inb(PIC_MASTER_POLL);
spin_unlock(&i8259A_lock);
}
-#endif

global_clock_event->event_handler(global_clock_event);

Index: linux-2.6/arch/x86/kernel/time_64.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/time_64.c
+++ linux-2.6/arch/x86/kernel/time_64.c
@@ -50,6 +50,20 @@ static irqreturn_t timer_interrupt(int i
{
inc_irq_stat(irq0_irqs);

+ /* Optimized out for !IO_APIC and x86_64 */
+ if (timer_ack) {
+ /*
+ * Subtle, when I/O APICs are used we have to ack timer IRQ
+ * manually to deassert NMI lines for the watchdog if run
+ * on an 82489DX-based system.
+ */
+ spin_lock(&i8259A_lock);
+ outb(0x0c, PIC_MASTER_OCW3);
+ /* Ack the IRQ; AEOI will end it automatically. */
+ inb(PIC_MASTER_POLL);
+ spin_unlock(&i8259A_lock);
+ }
+
global_clock_event->event_handler(global_clock_event);

#ifdef CONFIG_MCA