linux-kernel - [PATCH v4 1/5] cpufreq: Don't wait for CPU to going offline to restart governor

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Date:	Thu, 24 Jul 2014 18:07:24 -0700
From:	Saravana Kannan <skannan@...eaurora.org>
To:	"Rafael J . Wysocki" <rjw@...ysocki.net>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	Todd Poynor <toddpoynor@...gle.com>,
	"Srivatsa S . Bhat" <srivatsa@....edu>
Cc:	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-msm@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	"Saravana Kannan" <skannan@...eaurora.org>,
	Stephen Boyd <sboyd@...eaurora.org>
Subject: [PATCH v4 1/5] cpufreq: Don't wait for CPU to going offline to restart governor

There's no need to wait for the CPU going down to fully go offline to
restart the governor. We can stop the governor, change policy->cpus and
immediately restart the governor. This should reduce the time without any
CPUfreq monitoring and also help future patches with simplifying the code.

Signed-off-by: Saravana Kannan <skannan@...eaurora.org>
---
 drivers/cpufreq/cpufreq.c | 33 ++++++++++++++++++---------------
 1 file changed, 18 insertions(+), 15 deletions(-)

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 62259d2..ee0eb7b 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -1390,6 +1390,21 @@ static int __cpufreq_remove_dev_prepare(struct device *dev,
 		cpufreq_driver->stop_cpu(policy);
 	}
 
+	down_write(&policy->rwsem);
+	cpumask_clear_cpu(cpu, policy->cpus);
+	up_write(&policy->rwsem);
+
+	if (cpus > 1 && has_target()) {
+		ret = __cpufreq_governor(policy, CPUFREQ_GOV_START);
+		if (!ret)
+			ret = __cpufreq_governor(policy, CPUFREQ_GOV_LIMITS);
+
+		if (ret) {
+			pr_err("%s: Failed to start governor\n", __func__);
+			return ret;
+		}
+	}
+
 	return 0;
 }
 
@@ -1410,15 +1425,12 @@ static int __cpufreq_remove_dev_finish(struct device *dev,
 		return -EINVAL;
 	}
 
-	down_write(&policy->rwsem);
+	down_read(&policy->rwsem);
 	cpus = cpumask_weight(policy->cpus);
-
-	if (cpus > 1)
-		cpumask_clear_cpu(cpu, policy->cpus);
-	up_write(&policy->rwsem);
+	up_read(&policy->rwsem);
 
 	/* If cpu is last user of policy, free policy */
-	if (cpus == 1) {
+	if (cpus == 0) {
 		if (has_target()) {
 			ret = __cpufreq_governor(policy,
 					CPUFREQ_GOV_POLICY_EXIT);
@@ -1447,15 +1459,6 @@ static int __cpufreq_remove_dev_finish(struct device *dev,
 
 		if (!cpufreq_suspended)
 			cpufreq_policy_free(policy);
-	} else if (has_target()) {
-		ret = __cpufreq_governor(policy, CPUFREQ_GOV_START);
-		if (!ret)
-			ret = __cpufreq_governor(policy, CPUFREQ_GOV_LIMITS);
-
-		if (ret) {
-			pr_err("%s: Failed to start governor\n", __func__);
-			return ret;
-		}
 	}
 
 	per_cpu(cpufreq_cpu_data, cpu) = NULL;
-- 
1.8.2.1

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