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>

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index e6728bd61cc106fdd71f0ce7a4a025db020a1348..fd426500705370d607a5a5e2d6ddbc2f5992df11 100644 (file)
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -105,6 +105,9 @@ config GENERIC_TIME_VSYSCALL
        bool
        default X86_64
 
+config ARCH_HAS_CPU_RELAX
+       def_bool y
+
 config HAVE_SETUP_PER_CPU_AREA
        def_bool X86_64
 

diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
index fea71597b40a5fac92098083c992c659f4be7dd2..32488e6f76ab11c284f9e49fe97e47fcddd1ad16 100644 (file)
--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -1628,7 +1628,7 @@ struct cpuidle_driver acpi_idle_driver = {
  */
 static int acpi_processor_setup_cpuidle(struct acpi_processor *pr)
 {
-       int i, count = 0;
+       int i, count = CPUIDLE_DRIVER_STATE_START;
        struct acpi_processor_cx *cx;
        struct cpuidle_state *state;
        struct cpuidle_device *dev = &pr->power.dev;
@@ -1687,6 +1687,8 @@ static int acpi_processor_setup_cpuidle(struct acpi_processor *pr)
                }
 
                count++;
+               if (count == CPUIDLE_STATE_MAX)
+                       break;
        }
 
        dev->state_count = count;

diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
index 2a98d99cbd46075707c15572dff6ace4e6c602c3..2c4b2d47973e195cbb0422a9b539400a2ad5ef5e 100644 (file)
--- 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))) {

diff --git a/include/linux/cpuidle.h b/include/linux/cpuidle.h
index b0fd85ab9efb07efc8c39ef6e3857e29caa93dfb..385d45b616db2059e9aa71441b8e918ac11cac28 100644 (file)
--- a/include/linux/cpuidle.h
+++ b/include/linux/cpuidle.h
@@ -46,9 +46,10 @@ struct cpuidle_state {
 /* Idle State Flags */
 #define CPUIDLE_FLAG_TIME_VALID        (0x01) /* is residency time measurable? */
 #define CPUIDLE_FLAG_CHECK_BM  (0x02) /* BM activity will exit state */
-#define CPUIDLE_FLAG_SHALLOW   (0x10) /* low latency, minimal savings */
-#define CPUIDLE_FLAG_BALANCED  (0x20) /* medium latency, moderate savings */
-#define CPUIDLE_FLAG_DEEP      (0x40) /* high latency, large savings */
+#define CPUIDLE_FLAG_POLL      (0x10) /* no latency, no savings */
+#define CPUIDLE_FLAG_SHALLOW   (0x20) /* low latency, minimal savings */
+#define CPUIDLE_FLAG_BALANCED  (0x40) /* medium latency, moderate savings */
+#define CPUIDLE_FLAG_DEEP      (0x80) /* high latency, large savings */
 
 #define CPUIDLE_DRIVER_FLAGS_MASK (0xFFFF0000)
 
@@ -178,4 +179,10 @@ static inline void cpuidle_unregister_governor(struct cpuidle_governor *gov) { }
 
 #endif
 
+#ifdef CONFIG_ARCH_HAS_CPU_RELAX
+#define CPUIDLE_DRIVER_STATE_START     1
+#else
+#define CPUIDLE_DRIVER_STATE_START     0
+#endif
+
 #endif /* _LINUX_CPUIDLE_H */