[PATCH 4/5] cpufreq: Add start_cpu() and stop_cpu() callbacks

[Viresh Kumar <viresh.kumar@xxxxxxxxxx>]

On CPU hotplug, the cpufreq core doesn't call any driver specific
callback unless all the CPUs of a policy went away.

There is need for a callback to be called in such cases (for the CPPC
cpufreq driver) now. Reuse the existing stop_cpu() callback and add a
new one for start_cpu().

Signed-off-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
---
 Documentation/cpu-freq/cpu-drivers.rst |  7 +++++--
 drivers/cpufreq/cpufreq.c              | 11 ++++++++---
 include/linux/cpufreq.h                |  5 ++++-
 3 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/Documentation/cpu-freq/cpu-drivers.rst b/Documentation/cpu-freq/cpu-drivers.rst
index a697278ce190..15cfe42b4075 100644
--- a/Documentation/cpu-freq/cpu-drivers.rst
+++ b/Documentation/cpu-freq/cpu-drivers.rst
@@ -71,8 +71,11 @@ And optionally
  .exit - A pointer to a per-policy cleanup function called during
  CPU_POST_DEAD phase of cpu hotplug process.
 
- .stop_cpu - A pointer to a per-policy stop function called during
- CPU_DOWN_PREPARE phase of cpu hotplug process.
+ .start_cpu - A pointer to a per-policy per-cpu start function called
+ during CPU online phase.
+
+ .stop_cpu - A pointer to a per-policy per-cpu stop function called
+ during CPU offline phase.
 
  .suspend - A pointer to a per-policy suspend function which is called
  with interrupts disabled and _after_ the governor is stopped for the
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 802abc925b2a..fac2522be5c3 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -1119,6 +1119,10 @@ static int cpufreq_add_policy_cpu(struct cpufreq_policy *policy, unsigned int cp
 
 	cpumask_set_cpu(cpu, policy->cpus);
 
+	/* Do CPU specific initialization if required */
+	if (cpufreq_driver->start_cpu)
+		cpufreq_driver->start_cpu(policy, cpu);
+
 	if (has_target()) {
 		ret = cpufreq_start_governor(policy);
 		if (ret)
@@ -1581,6 +1585,10 @@ static int cpufreq_offline(unsigned int cpu)
 		policy->cpu = cpumask_any(policy->cpus);
 	}
 
+	/* Do CPU specific de-initialization if required */
+	if (cpufreq_driver->stop_cpu)
+		cpufreq_driver->stop_cpu(policy, cpu);
+
 	/* Start governor again for active policy */
 	if (!policy_is_inactive(policy)) {
 		if (has_target()) {
@@ -1597,9 +1605,6 @@ static int cpufreq_offline(unsigned int cpu)
 		policy->cdev = NULL;
 	}
 
-	if (cpufreq_driver->stop_cpu)
-		cpufreq_driver->stop_cpu(policy);
-
 	if (has_target())
 		cpufreq_exit_governor(policy);
 
diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
index 353969c7acd3..c281b3df4e2f 100644
--- a/include/linux/cpufreq.h
+++ b/include/linux/cpufreq.h
@@ -371,7 +371,10 @@ struct cpufreq_driver {
 	int		(*online)(struct cpufreq_policy *policy);
 	int		(*offline)(struct cpufreq_policy *policy);
 	int		(*exit)(struct cpufreq_policy *policy);
-	void		(*stop_cpu)(struct cpufreq_policy *policy);
+
+	/* CPU specific start/stop */
+	void		(*start_cpu)(struct cpufreq_policy *policy, unsigned int cpu);
+	void		(*stop_cpu)(struct cpufreq_policy *policy, unsigned int cpu);
 	int		(*suspend)(struct cpufreq_policy *policy);
 	int		(*resume)(struct cpufreq_policy *policy);
 
-- 
2.31.1.272.g89b43f80a514