linux-kernel - [PATCH V3 2/3] cpufreq: intel_pstate: Migrate away from ->stop

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Message-Id: <c31424b7962608eb13f946a665ba6848c4986856.1623986349.git.viresh.kumar@linaro.org>
Date:   Fri, 18 Jun 2021 08:52:36 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Rafael Wysocki <rjw@...ysocki.net>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Len Brown <lenb@...nel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>
Cc:     linux-pm@...r.kernel.org,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dirk Brandewie <dirk.brandewie@...il.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH V3 2/3] cpufreq: intel_pstate: Migrate away from ->stop_cpu() callback

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 to separately
call stop_cpu() for cpufreq drivers.

Migrate to using the exit() and offline() callbacks instead of
stop_cpu().

We need to clear util hook from both the callbacks, exit() and
offline(), since it is possible that only exit() gets called sometimes
(specially on errors) or both get called at other times.
intel_pstate_clear_update_util_hook() anyway have enough protection in
place if it gets called a second time and will return early then.

Cc: Dirk Brandewie <dirk.brandewie@...il.com>
Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
---
V2->V3:
- Update intel_pstate_cpu_offline() as well.
- Improved commit log.

 drivers/cpufreq/intel_pstate.c | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index 0e69dffd5a76..8f8a2d9d7daa 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -2335,6 +2335,8 @@ static int intel_pstate_cpu_offline(struct cpufreq_policy *policy)

 	pr_debug("CPU %d going offline\n", cpu->cpu);

+	intel_pstate_clear_update_util_hook(policy->cpu);
+
 	if (cpu->suspended)
 		return 0;

@@ -2374,17 +2376,12 @@ static int intel_pstate_cpu_online(struct cpufreq_policy *policy)
 	return 0;
 }

-static void intel_pstate_stop_cpu(struct cpufreq_policy *policy)
-{
-	pr_debug("CPU %d stopping\n", policy->cpu);
-
-	intel_pstate_clear_update_util_hook(policy->cpu);
-}
-
 static int intel_pstate_cpu_exit(struct cpufreq_policy *policy)
 {
 	pr_debug("CPU %d exiting\n", policy->cpu);

+	intel_pstate_clear_update_util_hook(policy->cpu);
+
 	policy->fast_switch_possible = false;

 	return 0;
@@ -2451,7 +2448,6 @@ static struct cpufreq_driver intel_pstate = {
 	.resume		= intel_pstate_resume,
 	.init		= intel_pstate_cpu_init,
 	.exit		= intel_pstate_cpu_exit,
-	.stop_cpu	= intel_pstate_stop_cpu,
 	.offline	= intel_pstate_cpu_offline,
 	.online		= intel_pstate_cpu_online,
 	.update_limits	= intel_pstate_update_limits,
-- 
2.31.1.272.g89b43f80a514