[PATCH] cpuidle: Add an addtional trace for demoted c-states

[John Mathew <john.mathew@intel.com>]

This patch enables tracing of c-states that the device
eventually goes in to, which might be different from what
the governor had retuned. This scenario occurs in platforms
like Intel Medfield. Power tools like pytimechart will be
able to display accurate c-state transitions with the help of
this trace.

Signed-off-by: John Mathew <john.mathew@intel.com>
---
 drivers/cpuidle/cpuidle.c    |    3 +++
 include/trace/events/power.h |   23 +++++++++++++++++++++++
 2 files changed, 26 insertions(+), 0 deletions(-)

diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
index d4c5423..3d787ef 100644
--- a/drivers/cpuidle/cpuidle.c
+++ b/drivers/cpuidle/cpuidle.c
@@ -110,6 +110,9 @@ int cpuidle_idle_call(void)
 
 	dev->last_residency = target_state->enter(dev, target_state);
 
+	if (dev->last_state != target_state)
+		trace_power_demoted(POWER_CSTATE, dev->last_state->name, dev->cpu);
+
 	trace_power_end(dev->cpu);
 	trace_cpu_idle(PWR_EVENT_EXIT, dev->cpu);
 
diff --git a/include/trace/events/power.h b/include/trace/events/power.h
index 1bcc2a8..941dc1a 100644
--- a/include/trace/events/power.h
+++ b/include/trace/events/power.h
@@ -101,6 +101,29 @@ DEFINE_EVENT(power, power_start,
 	TP_ARGS(type, state, cpu_id)
 );
 
+TRACE_EVENT(power_demoted,
+
+	TP_PROTO(unsigned int type, char *state, unsigned int cpu_id),
+
+	TP_ARGS(type, state, cpu_id),
+
+	TP_STRUCT__entry(
+		__field(	u64,		type		)
+		__string(	state,		state		)
+		__field(	u64,		cpu_id		)
+	),
+
+	TP_fast_assign(
+		__entry->type = type;
+		__assign_str(state, state);
+		__entry->cpu_id = cpu_id;
+	),
+
+	TP_printk("type=%lu state=%s cpu_id=%lu", (unsigned long)__entry->type,
+		 __get_str(state), (unsigned long)__entry->cpu_id)
+
+);
+
 DEFINE_EVENT(power, power_frequency,
 
 	TP_PROTO(unsigned int type, unsigned int state, unsigned int cpu_id),
-- 
1.7.4.1

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