2 files changed, 15 insertions, 0 deletions

diff --git a/Documentation/cpu-freq/user-guide.txt b/Documentation/cpu-freq/user-guide.txt
index 917918f84fc7..75f41193f3e1 100644
--- a/Documentation/cpu-freq/user-guide.txt
+++ b/Documentation/cpu-freq/user-guide.txt
@@ -152,6 +152,18 @@ cpuinfo_min_freq :		this file shows the minimum operating
                                 frequency the processor can run at(in kHz) 
 cpuinfo_max_freq :              this file shows the maximum operating
                                 frequency the processor can run at(in kHz) 
+cpuinfo_transition_latency      The time it takes on this CPU to
+                                switch between two frequencies in nano
+                                seconds. If unknown or known to be
+                                that high that the driver does not
+                                work with the ondemand governor, -1
+                                (CPUFREQ_ETERNAL) will be returned.
+                                Using this information can be useful
+                                to choose an appropriate polling
+                                frequency for a kernel governor or
+                                userspace daemon. Make sure to not
+                                switch the frequency too often
+                                resulting in performance loss.
 scaling_driver :                this file shows what cpufreq driver is
                                 used to set the frequency on this CPU
 
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 1867dac35aff..6fe466efb0b5 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -452,6 +452,7 @@ static ssize_t show_##file_name				\
 
 show_one(cpuinfo_min_freq, cpuinfo.min_freq);
 show_one(cpuinfo_max_freq, cpuinfo.max_freq);
+show_one(cpuinfo_transition_latency, cpuinfo.transition_latency);
 show_one(scaling_min_freq, min);
 show_one(scaling_max_freq, max);
 show_one(scaling_cur_freq, cur);
@@ -659,6 +660,7 @@ __ATTR(_name, 0644, show_##_name, store_##_name)
 define_one_ro0400(cpuinfo_cur_freq);
 define_one_ro(cpuinfo_min_freq);
 define_one_ro(cpuinfo_max_freq);
+define_one_ro(cpuinfo_transition_latency);
 define_one_ro(scaling_available_governors);
 define_one_ro(scaling_driver);
 define_one_ro(scaling_cur_freq);
@@ -672,6 +674,7 @@ define_one_rw(scaling_setspeed);
 static struct attribute *default_attrs[] = {
         &cpuinfo_min_freq.attr,
         &cpuinfo_max_freq.attr,
+        &cpuinfo_transition_latency.attr,
         &scaling_min_freq.attr,
         &scaling_max_freq.attr,
         &affected_cpus.attr,