[PATCH V4 0/4] cpufreq: Migrate away from ->stop_cpu() callback

Hi Rafael,

These are based on your patch [1] now.

commit 367dc4aa932b ("cpufreq: Add stop CPU callback to cpufreq_driver
interface") added the stop_cpu() callback to allow the drivers to do
clean up before the CPU is completely down and its state can't be
modified.

At that time the CPU hotplug framework used to call the cpufreq core's
registered notifier for different events like CPU_DOWN_PREPARE and
CPU_POST_DEAD. The stop_cpu() callback was called during the
CPU_DOWN_PREPARE event.

This is no longer the case, cpuhp_cpufreq_offline() is called only once
by the CPU hotplug core now and we don't really need two separate
callbacks for cpufreq drivers, i.e. stop_cpu() and exit(), as everything
can be done from the exit() callback itself.

Migrate to using the offline() or exit() callback instead of stop_cpu().

V3->V4:
- Based on a cleanup patch [1] from Rafael, apart from 5.13-rc7.
- No need to update exit() for intel pstate anymore.
- Remove the stop_cpu() callback completely.

--
Viresh

[1] https://lore.kernel.org/linux-pm/5490292.DvuYhMxLoT@kreacher/

Viresh Kumar (4):
  cpufreq: cppc: Migrate to ->exit() callback instead of ->stop_cpu()
  cpufreq: intel_pstate: Migrate to ->offline() instead of ->stop_cpu()
  cpufreq: powerenv: Migrate to ->exit() callback instead of
    ->stop_cpu()
  cpufreq: Remove stop_cpu() callback

 Documentation/cpu-freq/cpu-drivers.rst        |  3 --
 .../zh_CN/cpu-freq/cpu-drivers.rst            |  3 --
 drivers/cpufreq/cppc_cpufreq.c                | 46 ++++++++++---------
 drivers/cpufreq/cpufreq.c                     |  3 --
 drivers/cpufreq/intel_pstate.c                | 10 +---
 drivers/cpufreq/powernv-cpufreq.c             | 23 ++++------
 include/linux/cpufreq.h                       |  1 -
 7 files changed, 35 insertions(+), 54 deletions(-)

-- 
2.31.1.272.g89b43f80a514

commit 367dc4aa932b ("cpufreq: Add stop CPU callback to cpufreq_driver
interface") added the stop_cpu() callback to allow the drivers to do
clean up before the CPU is completely down and its state can't be
modified.

At that time the CPU hotplug framework used to call the cpufreq core's
registered notifier for different events like CPU_DOWN_PREPARE and
CPU_POST_DEAD. The stop_cpu() callback was called during the
CPU_DOWN_PREPARE event.

This is no longer the case, cpuhp_cpufreq_offline() is called only once
by the CPU hotplug core now and we don't really need two separate
callbacks for cpufreq drivers, i.e. stop_cpu() and exit(), as everything
can be done from the exit() callback itself.

Migrate to using the exit() callback instead of stop_cpu().

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
---
 drivers/cpufreq/powernv-cpufreq.c | 23 +++++++++--------------
 1 file changed, 9 insertions(+), 14 deletions(-)

diff --git a/drivers/cpufreq/powernv-cpufreq.c b/drivers/cpufreq/powernv-cpufreq.c
index e439b43c19eb..005600cef273 100644
--- a/drivers/cpufreq/powernv-cpufreq.c
+++ b/drivers/cpufreq/powernv-cpufreq.c

@@ -875,7 +875,15 @@ static int powernv_cpufreq_cpu_init(struct cpufreq_policy *policy)
 
 static int powernv_cpufreq_cpu_exit(struct cpufreq_policy *policy)
 {
-	/* timer is deleted in cpufreq_cpu_stop() */
+	struct powernv_smp_call_data freq_data;
+	struct global_pstate_info *gpstates = policy->driver_data;
+
+	freq_data.pstate_id = idx_to_pstate(powernv_pstate_info.min);
+	freq_data.gpstate_id = idx_to_pstate(powernv_pstate_info.min);
+	smp_call_function_single(policy->cpu, set_pstate, &freq_data, 1);
+	if (gpstates)
+		del_timer_sync(&gpstates->timer);
+
 	kfree(policy->driver_data);
 
 	return 0;

@@ -1007,18 +1015,6 @@ static struct notifier_block powernv_cpufreq_opal_nb = {
 	.priority	= 0,
 };
 
-static void powernv_cpufreq_stop_cpu(struct cpufreq_policy *policy)
-{
-	struct powernv_smp_call_data freq_data;
-	struct global_pstate_info *gpstates = policy->driver_data;
-
-	freq_data.pstate_id = idx_to_pstate(powernv_pstate_info.min);
-	freq_data.gpstate_id = idx_to_pstate(powernv_pstate_info.min);
-	smp_call_function_single(policy->cpu, set_pstate, &freq_data, 1);
-	if (gpstates)
-		del_timer_sync(&gpstates->timer);
-}
-
 static unsigned int powernv_fast_switch(struct cpufreq_policy *policy,
 					unsigned int target_freq)
 {

@@ -1042,7 +1038,6 @@ static struct cpufreq_driver powernv_cpufreq_driver = {
 	.target_index	= powernv_cpufreq_target_index,
 	.fast_switch	= powernv_fast_switch,
 	.get		= powernv_cpufreq_get,
-	.stop_cpu	= powernv_cpufreq_stop_cpu,
 	.attr		= powernv_cpu_freq_attr,
 };
 

-- 
2.31.1.272.g89b43f80a514

Viresh Kumar [off-list ref] writes:

Subject: Re: [PATCH V4 3/4] cpufreq: powerenv: Migrate to ->exit() callback instead of ->stop_cpu()

Typo in subject should be "powernv".

cheers

commit 367dc4aa932b ("cpufreq: Add stop CPU callback to cpufreq_driver
interface") added the stop_cpu() callback to allow the drivers to do
clean up before the CPU is completely down and its state can't be
modified.

At that time the CPU hotplug framework used to call the cpufreq core's
registered notifier for different events like CPU_DOWN_PREPARE and
CPU_POST_DEAD. The stop_cpu() callback was called during the
CPU_DOWN_PREPARE event.

This is no longer the case, cpuhp_cpufreq_offline() is called only once
by the CPU hotplug core now and we don't really need two separate
callbacks for cpufreq drivers, i.e. stop_cpu() and exit(), as everything
can be done from the exit() callback itself.

Migrate to using the exit() callback instead of stop_cpu().

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
---
V4->V4.1:
- s/powerenv/powernv/

 drivers/cpufreq/powernv-cpufreq.c | 23 +++++++++--------------
 1 file changed, 9 insertions(+), 14 deletions(-)

diff --git a/drivers/cpufreq/powernv-cpufreq.c b/drivers/cpufreq/powernv-cpufreq.c
index e439b43c19eb..005600cef273 100644
--- a/drivers/cpufreq/powernv-cpufreq.c
+++ b/drivers/cpufreq/powernv-cpufreq.c

@@ -875,7 +875,15 @@ static int powernv_cpufreq_cpu_init(struct cpufreq_policy *policy)
 
 static int powernv_cpufreq_cpu_exit(struct cpufreq_policy *policy)
 {
-	/* timer is deleted in cpufreq_cpu_stop() */
+	struct powernv_smp_call_data freq_data;
+	struct global_pstate_info *gpstates = policy->driver_data;
+
+	freq_data.pstate_id = idx_to_pstate(powernv_pstate_info.min);
+	freq_data.gpstate_id = idx_to_pstate(powernv_pstate_info.min);
+	smp_call_function_single(policy->cpu, set_pstate, &freq_data, 1);
+	if (gpstates)
+		del_timer_sync(&gpstates->timer);
+
 	kfree(policy->driver_data);
 
 	return 0;

@@ -1007,18 +1015,6 @@ static struct notifier_block powernv_cpufreq_opal_nb = {
 	.priority	= 0,
 };
 
-static void powernv_cpufreq_stop_cpu(struct cpufreq_policy *policy)
-{
-	struct powernv_smp_call_data freq_data;
-	struct global_pstate_info *gpstates = policy->driver_data;
-
-	freq_data.pstate_id = idx_to_pstate(powernv_pstate_info.min);
-	freq_data.gpstate_id = idx_to_pstate(powernv_pstate_info.min);
-	smp_call_function_single(policy->cpu, set_pstate, &freq_data, 1);
-	if (gpstates)
-		del_timer_sync(&gpstates->timer);
-}
-
 static unsigned int powernv_fast_switch(struct cpufreq_policy *policy,
 					unsigned int target_freq)
 {

@@ -1042,7 +1038,6 @@ static struct cpufreq_driver powernv_cpufreq_driver = {
 	.target_index	= powernv_cpufreq_target_index,
 	.fast_switch	= powernv_fast_switch,
 	.get		= powernv_cpufreq_get,
-	.stop_cpu	= powernv_cpufreq_stop_cpu,
 	.attr		= powernv_cpu_freq_attr,
 };
 

-- 
2.31.1.272.g89b43f80a514

On 23-06-21, 15:45, Michael Ellerman wrote:

Viresh Kumar [off-list ref] writes:

quoted

Subject: Re: [PATCH V4 3/4] cpufreq: powerenv: Migrate to ->exit() callback instead of ->stop_cpu()

Typo in subject should be "powernv".

Thanks for noticing it :)

-- 
viresh