idle: Implement generic idle function

All idle functions in arch/* are more or less the same, plus minus a
few bugs and extra instrumentation, tickless support and other
optional items.

Implement a generic idle function which resembles the functionality
found in arch/. Provide weak arch_cpu_idle_* functions which can be
overridden by the architecture code if needed.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Reviewed-by: Cc: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Cc: Magnus Damm <magnus.damm@gmail.com>
Link: http://lkml.kernel.org/r/20130321215233.646635455@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

3 files changed, 116 insertions, 0 deletions

diff --git a/arch/Kconfig b/arch/Kconfig
index 1455579791ec..a699f3767be4 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -216,6 +216,9 @@ config USE_GENERIC_SMP_HELPERS
 config GENERIC_SMP_IDLE_THREAD
        bool
 
+config GENERIC_IDLE_LOOP
+       bool
+
 # Select if arch init_task initializer is different to init/init_task.c
 config ARCH_INIT_TASK
        bool
diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index 7419e30c55fb..c6f6e0839b61 100644
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -220,4 +220,12 @@ enum cpuhp_state {
 void cpu_startup_entry(enum cpuhp_state state);
 void cpu_idle(void);
 
+void cpu_idle_poll_ctrl(bool enable);
+
+void arch_cpu_idle(void);
+void arch_cpu_idle_prepare(void);
+void arch_cpu_idle_enter(void);
+void arch_cpu_idle_exit(void);
+void arch_cpu_idle_dead(void);
+
 #endif /* _LINUX_CPU_H_ */
diff --git a/kernel/cpu/idle.c b/kernel/cpu/idle.c
index 1908f00e0e98..54c320383934 100644
--- a/kernel/cpu/idle.c
+++ b/kernel/cpu/idle.c
@@ -3,8 +3,113 @@
  */
 #include <linux/sched.h>
 #include <linux/cpu.h>
+#include <linux/tick.h>
+#include <linux/mm.h>
 
+#include <asm/tlb.h>
+
+#include <trace/events/power.h>
+
+#ifndef CONFIG_GENERIC_IDLE_LOOP
 void cpu_startup_entry(enum cpuhp_state state)
 {
         cpu_idle();
 }
+#else
+
+static int __read_mostly cpu_idle_force_poll;
+
+void cpu_idle_poll_ctrl(bool enable)
+{
+        if (enable) {
+                cpu_idle_force_poll++;
+        } else {
+                cpu_idle_force_poll--;
+                WARN_ON_ONCE(cpu_idle_force_poll < 0);
+        }
+}
+
+#ifdef CONFIG_GENERIC_IDLE_POLL_SETUP
+static int __init cpu_idle_poll_setup(char *__unused)
+{
+        cpu_idle_force_poll = 1;
+        return 1;
+}
+__setup("nohlt", cpu_idle_poll_setup);
+
+static int __init cpu_idle_nopoll_setup(char *__unused)
+{
+        cpu_idle_force_poll = 0;
+        return 1;
+}
+__setup("hlt", cpu_idle_nopoll_setup);
+#endif
+
+static inline int cpu_idle_poll(void)
+{
+        trace_cpu_idle_rcuidle(0, smp_processor_id());
+        local_irq_enable();
+        while (!need_resched())
+                cpu_relax();
+        trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, smp_processor_id());
+        return 1;
+}
+
+/* Weak implementations for optional arch specific functions */
+void __weak arch_cpu_idle_prepare(void) { }
+void __weak arch_cpu_idle_enter(void) { }
+void __weak arch_cpu_idle_exit(void) { }
+void __weak arch_cpu_idle_dead(void) { }
+void __weak arch_cpu_idle(void)
+{
+        cpu_idle_force_poll = 1;
+}
+
+/*
+ * Generic idle loop implementation
+ */
+static void cpu_idle_loop(void)
+{
+        while (1) {
+                tick_nohz_idle_enter();
+
+                while (!need_resched()) {
+                        check_pgt_cache();
+                        rmb();
+
+                        if (cpu_is_offline(smp_processor_id()))
+                                arch_cpu_idle_dead();
+
+                        local_irq_disable();
+                        arch_cpu_idle_enter();
+
+                        if (cpu_idle_force_poll) {
+                                cpu_idle_poll();
+                        } else {
+                                current_clr_polling();
+                                if (!need_resched()) {
+                                        stop_critical_timings();
+                                        rcu_idle_enter();
+                                        arch_cpu_idle();
+                                        WARN_ON_ONCE(irqs_disabled());
+                                        rcu_idle_exit();
+                                        start_critical_timings();
+                                } else {
+                                        local_irq_enable();
+                                }
+                                current_set_polling();
+                        }
+                        arch_cpu_idle_exit();
+                }
+                tick_nohz_idle_exit();
+                schedule_preempt_disabled();
+        }
+}
+
+void cpu_startup_entry(enum cpuhp_state state)
+{
+        current_set_polling();
+        arch_cpu_idle_prepare();
+        cpu_idle_loop();
+}
+#endif