linux-kernel - [PATCH] PM / devfreq: mediatek: protect oop in critical session

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Date:   Fri, 18 Aug 2023 10:17:41 +0800
From:   Mark Tseng <chun-jen.tseng@...iatek.com>
To:     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>, <devicetree@...r.kernel.org>,
        <Project_Global_Chrome_Upstream_Group@...iatek.com>,
        <chun-jen.tseng@...iatek.com>
Subject: [PATCH] PM / devfreq: mediatek: protect oop in critical session

mtk_ccifreq_opp_notifier is reenter function when policy0 / policy6
change freq, so metex_lock should protect all OPP event.

Signed-off-by: Mark Tseng <chun-jen.tseng@...iatek.com>
---
 drivers/devfreq/mtk-cci-devfreq.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/devfreq/mtk-cci-devfreq.c b/drivers/devfreq/mtk-cci-devfreq.c
index 83a73f0ccd80..b0ed25e33f2b 100644
--- a/drivers/devfreq/mtk-cci-devfreq.c
+++ b/drivers/devfreq/mtk-cci-devfreq.c
@@ -137,6 +137,8 @@ static int mtk_ccifreq_target(struct device *dev, unsigned long *freq,
 	if (drv->pre_freq == *freq)
 		return 0;
 
+	mutex_lock(&drv->reg_lock);
+
 	inter_voltage = drv->inter_voltage;
 	cci_pll = clk_get_parent(drv->cci_clk);
 
@@ -147,8 +149,6 @@ static int mtk_ccifreq_target(struct device *dev, unsigned long *freq,
 		return PTR_ERR(opp);
 	}
 
-	mutex_lock(&drv->reg_lock);
-
 	voltage = dev_pm_opp_get_voltage(opp);
 	dev_pm_opp_put(opp);
 
@@ -227,9 +227,9 @@ static int mtk_ccifreq_opp_notifier(struct notifier_block *nb,
 	drv = container_of(nb, struct mtk_ccifreq_drv, opp_nb);
 
 	if (event == OPP_EVENT_ADJUST_VOLTAGE) {
+		mutex_lock(&drv->reg_lock);
 		freq = dev_pm_opp_get_freq(opp);
 
-		mutex_lock(&drv->reg_lock);
 		/* current opp item is changed */
 		if (freq == drv->pre_freq) {
 			volt = dev_pm_opp_get_voltage(opp);
-- 
2.18.0