The some of the existing ARM CPU "wait for interrupt" implementations

were buggy - they'd test hlt_counter/need_resched with interrupts
enabled, and then go to sleep.  An interrupt could be received between
the test and sleeping, and we could have 10ms latency before we ran
a task.  This changeset fixes this by providing a generic "cpu idle"
wrapper that handles these issues.

arch/arm/kernel/process.c

@@ -31,14 +31,6 @@
 #include <asm/processor.h>
 #include <asm/uaccess.h>
 
-/*
- * Values for cpu_do_idle()
- */
-#define IDLE_WAIT_SLOW	0
-#define IDLE_WAIT_FAST	1
-#define IDLE_CLOCK_SLOW	2
-#define IDLE_CLOCK_FAST	3
-
 extern const char *processor_modes[];
 extern void setup_mm_for_reboot(char mode);
 
@@ -77,6 +69,18 @@ __setup("hlt", hlt_setup);
 void (*pm_idle)(void);
 void (*pm_power_off)(void);
 
+/*
+ * This is our default idle handler.  We need to disable
+ * interrupts here to ensure we don't miss a wakeup call.
+ */
+static void default_idle(void)
+{
+	__cli();
+	if (!need_resched() && !hlt_counter)
+		arch_idle();
+	__sti();
+}
+
 /*
  * The idle thread.  We try to conserve power, while trying to keep
  * overall latency low.  The architecture specific idle is passed
@@ -89,7 +93,7 @@ void cpu_idle(void)
 	while (1) {
 		void (*idle)(void) = pm_idle;
 		if (!idle)
-			idle = arch_idle;
+			idle = default_idle;
 		leds_event(led_idle_start);
 		while (!need_resched())
 			idle();

include/asm-arm/arch-adifcc/system.h

@@ -11,8 +11,7 @@
 static inline void arch_idle(void)
 {
 #if 0
-	if (!hlt_counter)
-		cpu_do_idle(0);
+	cpu_do_idle();
 #endif
 }
 

include/asm-arm/arch-anakin/system.h

@@ -15,8 +15,7 @@
 #ifndef __ASM_ARCH_SYSTEM_H
 #define __ASM_ARCH_SYSTEM_H
 
-static inline void
-arch_idle(void)
+static inline void arch_idle(void)
 {
 }
 

include/asm-arm/arch-arc/system.h

@@ -8,9 +8,8 @@
  * published by the Free Software Foundation.
  */
 
-static void arch_idle(void)
+static inline void arch_idle(void)
 {
-	while (!need_resched() && !hlt_counter);
 }
 
 static inline void arch_reset(char mode)

include/asm-arm/arch-cl7500/system.h

@@ -7,11 +7,11 @@
 #define __ASM_ARCH_SYSTEM_H
 
 #include <asm/hardware/iomd.h>
+#include <asm/io.h>
 
-static void arch_idle(void)
+static inline void arch_idle(void)
 {
-	while (!need_resched() && !hlt_counter)
-		iomd_writeb(0, IOMD_SUSMODE);
+	iomd_writeb(0, IOMD_SUSMODE);
 }
 
 #define arch_reset(mode)			\

include/asm-arm/arch-clps711x/system.h

@@ -22,7 +22,7 @@
 
 #include <asm/hardware/clps7111.h>
 
-static void arch_idle(void)
+static inline void arch_idle(void)
 {
 	clps_writel(1, HALT);
 	__asm__ __volatile__(

include/asm-arm/arch-ebsa110/system.h

@@ -20,31 +20,18 @@
  * Instead, we spin, polling the IRQ_STAT register for the occurrence
  * of any interrupt with core clock down to the memory clock.
  */
-static void arch_idle(void)
+static inline void arch_idle(void)
 {
 	const char *irq_stat = (char *)0xff000000;
-	long flags;
 
-	if (!hlt_counter)
-		return;
+	/* disable clock switching */
+	asm volatile ("mcr%? p15, 0, ip, c15, c2, 2");
 
-	do {
-		/* disable interrupts */
-		cli();
-		/* check need_resched here to avoid races */
-		if (need_resched()) {
-			sti();
-			return;
-		}
-		/* disable clock switching */
-		asm volatile ("mcr%? p15, 0, ip, c15, c2, 2");
-		/* wait for an interrupt to occur */
-		while (!*irq_stat);
-		/* enable clock switching */
-		asm volatile ("mcr%? p15, 0, ip, c15, c1, 2");
-		/* allow the interrupt to happen */
-		sti();
-	} while (!need_resched());
+	/* wait for an interrupt to occur */
+	while (!*irq_stat);
+
+	/* enable clock switching */
+	asm volatile ("mcr%? p15, 0, ip, c15, c1, 2");
 }
 
 #define arch_reset(mode)	cpu_reset(0x80000000)

include/asm-arm/arch-ebsa285/system.h

@@ -13,26 +13,9 @@
 #include <asm/leds.h>
 #include <asm/mach-types.h>
 
-static void arch_idle(void)
+static inline void arch_idle(void)
 {
-	unsigned long start_idle;
-
-	start_idle = jiffies;
-
-	do {
-		if (need_resched() || hlt_counter)
-			goto slow_out;
-		cpu_do_idle(IDLE_WAIT_FAST);
-	} while (time_before(jiffies, start_idle + HZ/50));
-
-	cpu_do_idle(IDLE_CLOCK_SLOW);
-
-	while (!need_resched() && !hlt_counter) {
-		cpu_do_idle(IDLE_WAIT_SLOW);
-	}
-
-	cpu_do_idle(IDLE_CLOCK_FAST);
-slow_out:
+	cpu_do_idle();
 }
 
 static inline void arch_reset(char mode)

include/asm-arm/arch-epxa10db/system.h

@@ -24,13 +24,13 @@
 
 #include <asm/arch/platform.h>
 
-static void arch_idle(void)
+static inline void arch_idle(void)
 {
 	/*
 	 * This should do all the clock switching
 	 * and wait for interrupt tricks
 	 */
-	cpu_do_idle(0);
+	cpu_do_idle();
 }
 
 extern __inline__ void arch_reset(char mode)

include/asm-arm/arch-integrator/system.h

@@ -23,13 +23,13 @@
 
 #include <asm/arch/platform.h>
 
-static void arch_idle(void)
+static inline void arch_idle(void)
 {
 	/*
 	 * This should do all the clock switching
 	 * and wait for interrupt tricks
 	 */
-	cpu_do_idle(0);
+	cpu_do_idle();
 }
 
 static inline void arch_reset(char mode)

include/asm-arm/arch-iop310/system.h

@@ -10,10 +10,7 @@
 
 static inline void arch_idle(void)
 {
-	if (!hlt_counter)
-	{
-		cpu_do_idle(0);
-	}
+	cpu_do_idle();
 }
 
 

include/asm-arm/arch-l7200/system.h

@@ -12,9 +12,8 @@
 #ifndef __ASM_ARCH_SYSTEM_H
 #define __ASM_ARCH_SYSTEM_H
 
-static void arch_idle(void)
+static inline void arch_idle(void)
 {
-	/* fixme: this needs to be cleaned up (converted from ASM code) --rmk */
 	*(unsigned long *)(IO_BASE + 0x50004) = 1;	/* idle mode */
 }
 

include/asm-arm/arch-nexuspci/system.h

@@ -14,10 +14,9 @@
 #ifndef __ASM_ARCH_SYSTEM_H
 #define __ASM_ARCH_SYSTEM_H
 
-static void arch_idle(void)
+static inline void arch_idle(void)
 {
-	while (!need_resched() && !hlt_counter)
-		cpu_do_idle(IDLE_WAIT_SLOW);
+	cpu_do_idle();
 }
 
 #define arch_reset(mode)	do { } while (0)

include/asm-arm/arch-pxa/system.h

@@ -14,13 +14,7 @@
 
 static inline void arch_idle(void)
 {
-	if (!hlt_counter) {
-		int flags;
-		local_irq_save(flags);
-		if(!need_resched())
-			cpu_do_idle(0);
-		local_irq_restore(flags);
-	}
+	cpu_do_idle();
 }
 
 

include/asm-arm/arch-rpc/system.h

@@ -11,26 +11,9 @@
 #include <asm/hardware/iomd.h>
 #include <asm/io.h>
 
-static void arch_idle(void)
+static inline void arch_idle(void)
 {
-	unsigned long start_idle;
-
-	start_idle = jiffies;
-
-	do {
-		if (need_resched() || hlt_counter)
-			goto slow_out;
-		cpu_do_idle(IDLE_WAIT_FAST);
-	} while (time_before(jiffies, start_idle + HZ/50));
-
-	cpu_do_idle(IDLE_CLOCK_SLOW);
-
-	while (!need_resched() && !hlt_counter) {
-		cpu_do_idle(IDLE_WAIT_SLOW);
-	}
-
-	cpu_do_idle(IDLE_CLOCK_FAST);
-slow_out:
+	cpu_do_idle();
 }
 
 static inline void arch_reset(char mode)

include/asm-arm/arch-sa1100/system.h

@@ -7,13 +7,7 @@
 
 static inline void arch_idle(void)
 {
-	if (!hlt_counter) {
-		int flags;
-		local_irq_save(flags);
-		if (!need_resched())
-			cpu_do_idle(0);
-		local_irq_restore(flags);
-	}
+	cpu_do_idle();
 }
 
 #ifdef CONFIG_SA1100_VICTOR

include/asm-arm/arch-shark/system.h

@@ -21,7 +21,7 @@ static void arch_reset(char mode)
 
 }
 
-static void arch_idle(void)
+static inline void arch_idle(void)
 {
 }
 

include/asm-arm/arch-tbox/system.h

@@ -6,26 +6,9 @@
 #ifndef __ASM_ARCH_SYSTEM_H
 #define __ASM_ARCH_SYSTEM_H
 
-static void arch_idle(void)
+static inline void arch_idle(void)
 {
-	unsigned long start_idle;
-
-	start_idle = jiffies;
-
-	do {
-		if (need_resched() || hlt_counter)
-			goto slow_out;
-		cpu_do_idle(IDLE_WAIT_FAST);
-	} while (time_before(jiffies, start_idle + HZ/50));
-
-	cpu_do_idle(IDLE_CLOCK_SLOW);
-
-	while (!need_resched() && !hlt_counter) {
-		cpu_do_idle(IDLE_WAIT_SLOW);
-	}
-
-	cpu_do_idle(IDLE_CLOCK_FAST);
-slow_out:
+	cpu_do_idle();
 }
 
 #define arch_reset(mode)	do { } while (0)

include/asm-arm/cpu-multi32.h

@@ -43,7 +43,7 @@ extern struct processor {
 	/*
 	 * Idle the processor
 	 */
-	int (*_do_idle)(int mode);
+	int (*_do_idle)(void);
 	/*
 	 * Processor architecture specific
 	 */
@@ -113,7 +113,7 @@ extern const struct processor sa110_processor_functions;
 #define cpu_proc_init()				processor._proc_init()
 #define cpu_proc_fin()				processor._proc_fin()
 #define cpu_reset(addr)				processor.reset(addr)
-#define cpu_do_idle(mode)			processor._do_idle(mode)
+#define cpu_do_idle()				processor._do_idle()
 
 #define cpu_cache_clean_invalidate_all()	processor.cache.clean_invalidate_all()
 #define cpu_cache_clean_invalidate_range(s,e,f)	processor.cache.clean_invalidate_range(s,e,f)

include/asm-arm/cpu-single.h

@@ -52,7 +52,7 @@ extern void cpu_data_abort(unsigned long pc);
 extern void cpu_check_bugs(void);
 extern void cpu_proc_init(void);
 extern void cpu_proc_fin(void);
-extern int cpu_do_idle(int mode);
+extern int cpu_do_idle(void);
 
 extern void cpu_cache_clean_invalidate_all(void);
 extern void cpu_cache_clean_invalidate_range(unsigned long address, unsigned long end, int flags);