[PATCH v2] devfreq: Add tracepoint for frequency changes

[Matthias Kaehlcke]

Add a tracepoint for frequency changes of devfreq devices and
use it.

Signed-off-by: Matthias Kaehlcke <m...@chromium.org>
---
(sending v2 without much delay wrt v1, since the change in devfreq
 probably isn't controversial, and I'll be offline a few days)

Changes in v2:
- included trace_devfreq_frequency_enabled() in the condition
  to avoid unnecessary evaluation when the trace point is
  disabled
---
 drivers/devfreq/devfreq.c      |  3 +++
 include/trace/events/devfreq.h | 18 ++++++++++++++++++
 2 files changed, 21 insertions(+)

diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index ab22bf8a12d6..e9f04dcafb01 100644
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c
@@ -317,6 +317,9 @@ static int devfreq_set_target(struct devfreq *devfreq, 
unsigned long new_freq,
 
        devfreq->previous_freq = new_freq;
 
+       if (trace_devfreq_frequency_enabled() && new_freq != cur_freq)
+               trace_devfreq_frequency(devfreq, new_freq);
+
        if (devfreq->suspend_freq)
                devfreq->resume_freq = cur_freq;
 
diff --git a/include/trace/events/devfreq.h b/include/trace/events/devfreq.h
index cf5b8772175d..a62d32fe3c33 100644
--- a/include/trace/events/devfreq.h
+++ b/include/trace/events/devfreq.h
@@ -8,6 +8,24 @@
 #include <linux/devfreq.h>
 #include <linux/tracepoint.h>
 
+TRACE_EVENT(devfreq_frequency,
+       TP_PROTO(struct devfreq *devfreq, unsigned long freq),
+
+       TP_ARGS(devfreq, freq),
+
+       TP_STRUCT__entry(
+               __string(dev_name, dev_name(&devfreq->dev))
+               __field(unsigned long, freq)
+       ),
+
+       TP_fast_assign(
+               __assign_str(dev_name, dev_name(&devfreq->dev));
+               __entry->freq = freq;
+       ),
+
+       TP_printk("dev_name=%s freq=%lu", __get_str(dev_name), __entry->freq)
+);
+
 TRACE_EVENT(devfreq_monitor,
        TP_PROTO(struct devfreq *devfreq),
 
-- 
2.23.0.237.gc6a4ce50a0-goog