intel_pstate: Add num_pstates to sysfs

Add a sysfs interface to display the total number of supported
pstates.  This value is independent of whether turbo has been
enabled or disabled.

Signed-off-by: Kristen Carlson Accardi <kristen@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

2 files changed, 17 insertions, 0 deletions

diff --git a/Documentation/cpu-freq/intel-pstate.txt b/Documentation/cpu-freq/intel-pstate.txt
index 7767ce6756be..655750743fb0 100644
--- a/Documentation/cpu-freq/intel-pstate.txt
+++ b/Documentation/cpu-freq/intel-pstate.txt
@@ -41,6 +41,10 @@ controlling P state selection. These files have been added to
       is supported by hardware that is in the turbo range.  This number
       is independent of whether turbo has been disabled or not.
 
+      num_pstates: displays the number of pstates that are supported
+      by hardware.  This number is independent of whether turbo has
+      been disabled or not.
+
 For contemporary Intel processors, the frequency is controlled by the
 processor itself and the P-states exposed to software are related to
 performance levels.  The idea that frequency can be set to a single
diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index ed6dd7dac094..80ecc351d613 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -354,6 +354,17 @@ static ssize_t show_turbo_pct(struct kobject *kobj,
         return sprintf(buf, "%u\n", turbo_pct);
 }
 
+static ssize_t show_num_pstates(struct kobject *kobj,
+                                struct attribute *attr, char *buf)
+{
+        struct cpudata *cpu;
+        int total;
+
+        cpu = all_cpu_data[0];
+        total = cpu->pstate.turbo_pstate - cpu->pstate.min_pstate + 1;
+        return sprintf(buf, "%u\n", total);
+}
+
 static ssize_t show_no_turbo(struct kobject *kobj,
                              struct attribute *attr, char *buf)
 {
@@ -435,12 +446,14 @@ define_one_global_rw(no_turbo);
 define_one_global_rw(max_perf_pct);
 define_one_global_rw(min_perf_pct);
 define_one_global_ro(turbo_pct);
+define_one_global_ro(num_pstates);
 
 static struct attribute *intel_pstate_attributes[] = {
         &no_turbo.attr,
         &max_perf_pct.attr,
         &min_perf_pct.attr,
         &turbo_pct.attr,
+        &num_pstates.attr,
         NULL
 };