linux-kernel - [PATCH v2 2/4] cpufreq: mediatek: using global lock avoid race condition

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Message-ID: <20241108063942.19744-3-chun-jen.tseng@mediatek.com>
Date: Fri, 8 Nov 2024 14:39:40 +0800
From: Mark Tseng <chun-jen.tseng@...iatek.com>
To: "Rafael J . Wysocki" <rafael@...nel.org>, Viresh Kumar
	<viresh.kumar@...aro.org>, MyungJoo Ham <myungjoo.ham@...sung.com>, "Kyungmin
 Park" <kyungmin.park@...sung.com>, Chanwoo Choi <cw00.choi@...sung.com>,
	Matthias Brugger <matthias.bgg@...il.com>, AngeloGioacchino Del Regno
	<angelogioacchino.delregno@...labora.com>
CC: <linux-pm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>, <linux-mediatek@...ts.infradead.org>,
	<Project_Global_Chrome_Upstream_Group@...iatek.com>,
	<chun-jen.tseng@...iatek.com>
Subject: [PATCH v2 2/4] cpufreq: mediatek: using global lock avoid race condition

In mtk_cpufreq_set_target() is re-enter function but the mutex lock
decalre in mtk_cpu_dvfs_info structure for each policy. It should
change to global variable for critical session avoid race condition
with 2 or more policy.

add mtk_cpufreq_get() replace cpufreq_generic_get() and use global lock
avoid return wrong clock.

Signed-off-by: Mark Tseng <chun-jen.tseng@...iatek.com>
---
 drivers/cpufreq/mediatek-cpufreq.c | 39 ++++++++++++++++++++++--------
 1 file changed, 29 insertions(+), 10 deletions(-)

diff --git a/drivers/cpufreq/mediatek-cpufreq.c b/drivers/cpufreq/mediatek-cpufreq.c
index f63183154e9a..6b3cd2b803bf 100644
--- a/drivers/cpufreq/mediatek-cpufreq.c
+++ b/drivers/cpufreq/mediatek-cpufreq.c
@@ -49,8 +49,6 @@ struct mtk_cpu_dvfs_info {
 	bool need_voltage_tracking;
 	int vproc_on_boot;
 	int pre_vproc;
-	/* Avoid race condition for regulators between notify and policy */
-	struct mutex reg_lock;
 	struct notifier_block opp_nb;
 	unsigned int opp_cpu;
 	unsigned long current_freq;
@@ -59,6 +57,9 @@ struct mtk_cpu_dvfs_info {
 	bool ccifreq_bound;
 };
 
+/* Avoid race condition for regulators between notify and policy */
+static DEFINE_MUTEX(mtk_policy_lock);
+
 static struct platform_device *cpufreq_pdev;
 
 static LIST_HEAD(dvfs_info_list);
@@ -209,12 +210,12 @@ static int mtk_cpufreq_set_target(struct cpufreq_policy *policy,
 	long freq_hz, pre_freq_hz;
 	int vproc, pre_vproc, inter_vproc, target_vproc, ret;
 
+	mutex_lock(&mtk_policy_lock);
+
 	inter_vproc = info->intermediate_voltage;
 
 	pre_freq_hz = clk_get_rate(cpu_clk);
 
-	mutex_lock(&info->reg_lock);
-
 	if (unlikely(info->pre_vproc <= 0))
 		pre_vproc = regulator_get_voltage(info->proc_reg);
 	else
@@ -308,7 +309,7 @@ static int mtk_cpufreq_set_target(struct cpufreq_policy *policy,
 	info->current_freq = freq_hz;
 
 out:
-	mutex_unlock(&info->reg_lock);
+	mutex_unlock(&mtk_policy_lock);
 
 	return ret;
 }
@@ -316,19 +317,20 @@ static int mtk_cpufreq_set_target(struct cpufreq_policy *policy,
 static int mtk_cpufreq_opp_notifier(struct notifier_block *nb,
 				    unsigned long event, void *data)
 {
-	struct dev_pm_opp *opp = data;
+	struct dev_pm_opp *opp;
 	struct dev_pm_opp *new_opp;
 	struct mtk_cpu_dvfs_info *info;
 	unsigned long freq, volt;
 	struct cpufreq_policy *policy;
 	int ret = 0;
 
+	mutex_lock(&mtk_policy_lock);
+	opp = data;
 	info = container_of(nb, struct mtk_cpu_dvfs_info, opp_nb);
 
 	if (event == OPP_EVENT_ADJUST_VOLTAGE) {
 		freq = dev_pm_opp_get_freq(opp);
 
-		mutex_lock(&info->reg_lock);
 		if (info->current_freq == freq) {
 			volt = dev_pm_opp_get_voltage(opp);
 			ret = mtk_cpufreq_set_voltage(info, volt);
@@ -336,7 +338,6 @@ static int mtk_cpufreq_opp_notifier(struct notifier_block *nb,
 				dev_err(info->cpu_dev,
 					"failed to scale voltage: %d\n", ret);
 		}
-		mutex_unlock(&info->reg_lock);
 	} else if (event == OPP_EVENT_DISABLE) {
 		freq = dev_pm_opp_get_freq(opp);
 
@@ -361,6 +362,7 @@ static int mtk_cpufreq_opp_notifier(struct notifier_block *nb,
 			}
 		}
 	}
+	mutex_unlock(&mtk_policy_lock);
 
 	return notifier_from_errno(ret);
 }
@@ -495,7 +497,6 @@ static int mtk_cpu_dvfs_info_init(struct mtk_cpu_dvfs_info *info, int cpu)
 	info->intermediate_voltage = dev_pm_opp_get_voltage(opp);
 	dev_pm_opp_put(opp);
 
-	mutex_init(&info->reg_lock);
 	info->current_freq = clk_get_rate(info->cpu_clk);
 
 	info->opp_cpu = cpu;
@@ -610,13 +611,31 @@ static void mtk_cpufreq_exit(struct cpufreq_policy *policy)
 	dev_pm_opp_free_cpufreq_table(info->cpu_dev, &policy->freq_table);
 }
 
+static unsigned int mtk_cpufreq_get(unsigned int cpu)
+{
+	struct mtk_cpu_dvfs_info *info;
+	unsigned long current_freq;
+
+	mutex_lock(&mtk_policy_lock);
+	info = mtk_cpu_dvfs_info_lookup(cpu);
+	if (!info) {
+		mutex_unlock(&mtk_policy_lock);
+		return 0;
+	}
+
+	current_freq = info->current_freq / 1000;
+	mutex_unlock(&mtk_policy_lock);
+
+	return current_freq;
+}
+
 static struct cpufreq_driver mtk_cpufreq_driver = {
 	.flags = CPUFREQ_NEED_INITIAL_FREQ_CHECK |
 		 CPUFREQ_HAVE_GOVERNOR_PER_POLICY |
 		 CPUFREQ_IS_COOLING_DEV,
 	.verify = cpufreq_generic_frequency_table_verify,
 	.target_index = mtk_cpufreq_set_target,
-	.get = cpufreq_generic_get,
+	.get = mtk_cpufreq_get,
 	.init = mtk_cpufreq_init,
 	.exit = mtk_cpufreq_exit,
 	.register_em = cpufreq_register_em_with_opp,
-- 
2.45.2