linux-kernel - [PATCH 1/2] soc: amlogic: meson-clk-measure: protect measure with a mutex

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Message-Id: <20190729130218.6635-2-narmstrong@baylibre.com>
Date:   Mon, 29 Jul 2019 15:02:17 +0200
From:   Neil Armstrong <narmstrong@...libre.com>
To:     khilman@...libre.com
Cc:     Neil Armstrong <narmstrong@...libre.com>,
        linux-arm-kernel@...ts.infradead.org,
        linux-amlogic@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>
Subject: [PATCH 1/2] soc: amlogic: meson-clk-measure: protect measure with a mutex

In order to protect clock measuring when multiple process asks for
a measure, protect the main measure function with mutexes.

Reviewed-by: Kevin Hilman <khilman@...libre.com>
Reviewed-by: Martin Blumenstingl <martin.blumenstingl@...glemail.com>
Signed-off-by: Neil Armstrong <narmstrong@...libre.com>
---
 drivers/soc/amlogic/meson-clk-measure.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/soc/amlogic/meson-clk-measure.c b/drivers/soc/amlogic/meson-clk-measure.c
index 19d4cbc93a17..c470e24f1dfa 100644
--- a/drivers/soc/amlogic/meson-clk-measure.c
+++ b/drivers/soc/amlogic/meson-clk-measure.c
@@ -11,6 +11,8 @@
 #include <linux/debugfs.h>
 #include <linux/regmap.h>
 
+static DEFINE_MUTEX(measure_lock);
+
 #define MSR_CLK_DUTY		0x0
 #define MSR_CLK_REG0		0x4
 #define MSR_CLK_REG1		0x8
@@ -360,6 +362,10 @@ static int meson_measure_id(struct meson_msr_id *clk_msr_id,
 	unsigned int val;
 	int ret;
 
+	ret = mutex_lock_interruptible(&measure_lock);
+	if (ret)
+		return ret;
+
 	regmap_write(priv->regmap, MSR_CLK_REG0, 0);
 
 	/* Set measurement duration */
@@ -377,8 +383,10 @@ static int meson_measure_id(struct meson_msr_id *clk_msr_id,
 
 	ret = regmap_read_poll_timeout(priv->regmap, MSR_CLK_REG0,
 				       val, !(val & MSR_BUSY), 10, 10000);
-	if (ret)
+	if (ret) {
+		mutex_unlock(&measure_lock);
 		return ret;
+	}
 
 	/* Disable */
 	regmap_update_bits(priv->regmap, MSR_CLK_REG0, MSR_ENABLE, 0);
@@ -386,6 +394,8 @@ static int meson_measure_id(struct meson_msr_id *clk_msr_id,
 	/* Get the value in multiple of gate time counts */
 	regmap_read(priv->regmap, MSR_CLK_REG2, &val);
 
+	mutex_unlock(&measure_lock);
+
 	if (val >= MSR_VAL_MASK)
 		return -EINVAL;
 
-- 
2.22.0