[PATCH] ia64: Interim pal_halt_light patch

While the sysctl variable is being worked out in the general kernel, here is
an interim patch which allows boot-time/dynamic control over the use of
PAL_HALT_LIGHT in the idle-loop.

arch/ia64/Kconfig

@@ -214,15 +214,6 @@ config FORCE_MAX_ZONEORDER
 	int
 	default "18"
 
-config IA64_PAL_IDLE
-	bool "Use PAL_HALT_LIGHT in idle loop"
-	help
-	  Say Y here to enable use of PAL_HALT_LIGHT in the cpu_idle loop.
-	  This allows the CPU to enter a low power state when idle.  You
-	  can enable CONFIG_IA64_PALINFO and check /proc/pal/cpu0/power_info
-	  to see the power consumption and latency for this state.  If you're
-	  unsure your firmware supports it, answer N.
-
 config SMP
 	bool "Symmetric multi-processing support"
 	help

arch/ia64/kernel/process.c

@@ -159,16 +159,25 @@ do_notify_resume_user (sigset_t *oldset, struct sigscratch *scr, long in_syscall
 		ia64_do_signal(oldset, scr, in_syscall);
 }
 
+static int pal_halt = 1;
+static int __init nohalt_setup(char * str)
+{
+	pal_halt = 0;
+	return 1;
+}
+__setup("nohalt", nohalt_setup);
+
 /*
  * We use this if we don't have any better idle routine..
  */
 void
 default_idle (void)
 {
-#ifdef CONFIG_IA64_PAL_IDLE
-	if (!need_resched())
-		safe_halt();
-#endif
+	unsigned long pmu_active = ia64_getreg(_IA64_REG_PSR) &
+				   (IA64_PSR_PP | IA64_PSR_UP);
+	while (!need_resched())
+		if (pal_halt && !pmu_active)
+			safe_halt();
 }
 
 void __attribute__((noreturn))