[RFC PATCH v2 7/8] cpuidle: introduce irq timing to make idle prediction

[Aubrey Li]

Introduce irq timings output as a factor to predict the duration
of the coming idle

Signed-off-by: Aubrey Li <aubrey...@linux.intel.com>
---
 drivers/cpuidle/Kconfig   |  1 +
 drivers/cpuidle/cpuidle.c | 17 ++++++++++++++++-
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/drivers/cpuidle/Kconfig b/drivers/cpuidle/Kconfig
index 7e48eb5..8b07e1c 100644
--- a/drivers/cpuidle/Kconfig
+++ b/drivers/cpuidle/Kconfig
@@ -5,6 +5,7 @@ config CPU_IDLE
        default y if ACPI || PPC_PSERIES
        select CPU_IDLE_GOV_LADDER if (!NO_HZ && !NO_HZ_IDLE)
        select CPU_IDLE_GOV_MENU if (NO_HZ || NO_HZ_IDLE)
+       select IRQ_TIMINGS
        help
          CPU idle is a generic framework for supporting software-controlled
          idle processor power management.  It includes modular cross-platform
diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
index 5d4f0b6..be56cea 100644
--- a/drivers/cpuidle/cpuidle.c
+++ b/drivers/cpuidle/cpuidle.c
@@ -22,6 +22,7 @@
 #include <linux/module.h>
 #include <linux/suspend.h>
 #include <linux/tick.h>
+#include <linux/interrupt.h>
 #include <trace/events/power.h>
 
 #include "cpuidle.h"
@@ -342,13 +343,27 @@ void cpuidle_entry_end(void)
 void cpuidle_predict(void)
 {
        struct cpuidle_device *dev = cpuidle_get_device();
-       unsigned int overhead_threshold;
+       unsigned int idle_interval, overhead_threshold;
+       u64 now, next_evt;
 
        if (!dev)
                return;
 
        overhead_threshold = dev->idle_stat.overhead * sysctl_fast_idle_ratio;
 
+       /*
+        * check irq timings if the next event is coming soon
+        */
+       now = local_clock();
+       local_irq_disable();
+       next_evt = irq_timings_next_event(now);
+       local_irq_enable();
+       idle_interval = div_u64(next_evt - now, NSEC_PER_USEC);
+       if (idle_interval < overhead_threshold) {
+               dev->idle_stat.fast_idle = true;
+               return;
+       }
+
        if (cpuidle_curr_governor->predict) {
                dev->idle_stat.predicted_us = cpuidle_curr_governor->predict();
                /*
-- 
2.7.4