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-rw-r--r--Documentation/cpu-freq/user-guide.txt12
-rw-r--r--drivers/cpufreq/cpufreq.c3
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,