cpuidle: Add a poll_idle method

Add a default poll idle state with 0 latency. Provides an option to users
to use poll_idle by using 0 as the latency requirement.

Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>

1 files changed, 41 insertions, 0 deletions

diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
index 2a98d99cbd46..2c4b2d47973e 100644
--- a/drivers/cpuidle/cpuidle.c
+++ b/drivers/cpuidle/cpuidle.c
@@ -15,6 +15,7 @@
 #include <linux/pm_qos_params.h>
 #include <linux/cpu.h>
 #include <linux/cpuidle.h>
+#include <linux/ktime.h>
 
 #include "cpuidle.h"
 
@@ -180,6 +181,44 @@ void cpuidle_disable_device(struct cpuidle_device *dev)
 
 EXPORT_SYMBOL_GPL(cpuidle_disable_device);
 
+#ifdef CONFIG_ARCH_HAS_CPU_RELAX
+static int poll_idle(struct cpuidle_device *dev, struct cpuidle_state *st)
+{
+        ktime_t t1, t2;
+        s64 diff;
+        int ret;
+
+        t1 = ktime_get();
+        local_irq_enable();
+        while (!need_resched())
+                cpu_relax();
+
+        t2 = ktime_get();
+        diff = ktime_to_us(ktime_sub(t2, t1));
+        if (diff > INT_MAX)
+                diff = INT_MAX;
+
+        ret = (int) diff;
+        return ret;
+}
+
+static void poll_idle_init(struct cpuidle_device *dev)
+{
+        struct cpuidle_state *state = &dev->states[0];
+
+        cpuidle_set_statedata(state, NULL);
+
+        snprintf(state->name, CPUIDLE_NAME_LEN, "C0 (poll idle)");
+        state->exit_latency = 0;
+        state->target_residency = 0;
+        state->power_usage = -1;
+        state->flags = CPUIDLE_FLAG_POLL | CPUIDLE_FLAG_TIME_VALID;
+        state->enter = poll_idle;
+}
+#else
+static void poll_idle_init(struct cpuidle_device *dev) {}
+#endif /* CONFIG_ARCH_HAS_CPU_RELAX */
+
 /**
  * cpuidle_register_device - registers a CPU's idle PM feature
  * @dev: the cpu
@@ -198,6 +237,8 @@ int cpuidle_register_device(struct cpuidle_device *dev)
 
         mutex_lock(&cpuidle_lock);
 
+        poll_idle_init(dev);
+
         per_cpu(cpuidle_devices, dev->cpu) = dev;
         list_add(&dev->device_list, &cpuidle_detected_devices);
         if ((ret = cpuidle_add_sysfs(sys_dev))) {