cpufreq: Add stop CPU callback to cpufreq_driver interface

This callback allows the driver to do clean up before the CPU is
completely down and its state cannot be modified.  This is used
by the intel_pstate driver to reduce the requested P state prior to
the core going away.  This is required because the requested P state
of the offline core is used to select the package P state. This
effectively sets the floor package P state to the requested P state on
the offline core.

Signed-off-by: Dirk Brandewie <dirk.j.brandewie@intel.com>
[rjw: Minor modifications]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

3 files changed, 10 insertions, 1 deletions

diff --git a/Documentation/cpu-freq/cpu-drivers.txt b/Documentation/cpu-freq/cpu-drivers.txt
index 8b1a4451422e..48da5fdcb9f1 100644
--- a/Documentation/cpu-freq/cpu-drivers.txt
+++ b/Documentation/cpu-freq/cpu-drivers.txt
@@ -61,7 +61,13 @@ target_index		-	See below on the differences.
 
 And optionally
 
-cpufreq_driver.exit -           A pointer to a per-CPU cleanup function.
+cpufreq_driver.exit -           A pointer to a per-CPU cleanup
+                                function called during CPU_POST_DEAD
+                                phase of cpu hotplug process.
+
+cpufreq_driver.stop_cpu -       A pointer to a per-CPU stop function
+                                called during CPU_DOWN_PREPARE phase of
+                                cpu hotplug process.
 
 cpufreq_driver.resume -         A pointer to a per-CPU resume function
                                 which is called with interrupts disabled
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 3c56c4759aa1..3aa7a7a226b3 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -1337,6 +1337,8 @@ static int __cpufreq_remove_dev_prepare(struct device *dev,
                                 pr_debug("%s: policy Kobject moved to cpu: %d from: %d\n",
                                          __func__, new_cpu, cpu);
                 }
+        } else if (cpufreq_driver->stop_cpu && cpufreq_driver->setpolicy) {
+                cpufreq_driver->stop_cpu(policy);
         }
 
         return 0;
diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
index 70929bcf1a9d..2d2e62c8666a 100644
--- a/include/linux/cpufreq.h
+++ b/include/linux/cpufreq.h
@@ -227,6 +227,7 @@ struct cpufreq_driver {
         int     (*bios_limit)   (int cpu, unsigned int *limit);
 
         int     (*exit)         (struct cpufreq_policy *policy);
+        void    (*stop_cpu)     (struct cpufreq_policy *policy);
         int     (*suspend)      (struct cpufreq_policy *policy);
         int     (*resume)       (struct cpufreq_policy *policy);
         struct freq_attr        **attr;