[ARM] idle: clean up pm_idle calling, obey hlt_counter

pm_idle is used by infrastructure (eg, cpuidle) which expects architectures
to call it in a certain way.  Arrange for ARM to follow x86's lead on this
and call pm_idle() with interrupts already disabled.  However, we expect
pm_idle() to enable interrupts before it returns.

Also, OMAP wants to be able to disable hlt-ing, so allow hlt_counter to
prevent all calls to pm_idle.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c
index 56820cc..39196df 100644 (file)
--- a/arch/arm/kernel/process.c
+++ b/arch/arm/kernel/process.c
@@ -114,9 +114,6 @@ void arm_machine_restart(char mode, const char *cmd)
 /*
  * Function pointers to optional machine specific functions
  */
-void (*pm_idle)(void);
-EXPORT_SYMBOL(pm_idle);
-
 void (*pm_power_off)(void);
 EXPORT_SYMBOL(pm_power_off);
 
@@ -130,20 +127,19 @@ EXPORT_SYMBOL_GPL(arm_pm_restart);
  */
 static void default_idle(void)
 {
-       if (hlt_counter)
-               cpu_relax();
-       else {
-               local_irq_disable();
-               if (!need_resched())
-                       arch_idle();
-               local_irq_enable();
-       }
+       if (!need_resched())
+               arch_idle();
+       local_irq_enable();
 }
 
+void (*pm_idle)(void) = default_idle;
+EXPORT_SYMBOL(pm_idle);
+
 /*
- * The idle thread.  We try to conserve power, while trying to keep
- * overall latency low.  The architecture specific idle is passed
- * a value to indicate the level of "idleness" of the system.
+ * The idle thread, has rather strange semantics for calling pm_idle,
+ * but this is what x86 does and we need to do the same, so that
+ * things like cpuidle get called in the same way.  The only difference
+ * is that we always respect 'hlt_counter' to prevent low power idle.
  */
 void cpu_idle(void)
 {
@@ -151,21 +147,31 @@ void cpu_idle(void)
 
        /* endless idle loop with no priority at all */
        while (1) {
-               void (*idle)(void) = pm_idle;
-
+               tick_nohz_stop_sched_tick(1);
+               leds_event(led_idle_start);
+               while (!need_resched()) {
 #ifdef CONFIG_HOTPLUG_CPU
-               if (cpu_is_offline(smp_processor_id())) {
-                       leds_event(led_idle_start);
-                       cpu_die();
-               }
+                       if (cpu_is_offline(smp_processor_id()))
+                               cpu_die();
 #endif
 
-               if (!idle)
-                       idle = default_idle;
-               leds_event(led_idle_start);
-               tick_nohz_stop_sched_tick(1);
-               while (!need_resched())
-                       idle();
+                       local_irq_disable();
+                       if (hlt_counter) {
+                               local_irq_enable();
+                               cpu_relax();
+                       } else {
+                               stop_critical_timings();
+                               pm_idle();
+                               start_critical_timings();
+                               /*
+                                * This will eventually be removed - pm_idle
+                                * functions should always return with IRQs
+                                * enabled.
+                                */
+                               WARN_ON(irqs_disabled());
+                               local_irq_enable();
+                       }
+               }
                leds_event(led_idle_end);
                tick_nohz_restart_sched_tick();
                preempt_enable_no_resched();