linux-kernel - [PATCH] hwmon: (sbtsi) Don't read sensor more than once if it doesn't respond

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Date:   Fri,  2 Apr 2021 00:45:42 +0300
From:   Konstantin Aladyshev <aladyshev22@...il.com>
To:     unlisted-recipients:; (no To-header on input)
Cc:     kunyi@...gle.com, aladyshev22@...il.com,
        Konstantin Aladyshev <aladyshev@...evt.ru>,
        Jean Delvare <jdelvare@...e.com>,
        Guenter Roeck <linux@...ck-us.net>,
        linux-hwmon@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] hwmon: (sbtsi) Don't read sensor more than once if it doesn't respond

From: Konstantin Aladyshev <aladyshev@...evt.ru>

SBTSI sensors don't work when the CPU is off.
In this case every 'i2c_smbus_read_byte_data' function would fail
by a timeout.
Currently temp1_max/temp1_min file reads can cause two such timeouts
for every read.
Restructure code so there will be no more than one timeout for every
read opeartion.

Signed-off-by: Konstantin Aladyshev <aladyshev@...evt.ru>
---
 drivers/hwmon/sbtsi_temp.c | 59 +++++++++++++++++++-------------------
 1 file changed, 29 insertions(+), 30 deletions(-)

diff --git a/drivers/hwmon/sbtsi_temp.c b/drivers/hwmon/sbtsi_temp.c
index e35357c48b8e..e09a8cf6de45 100644
--- a/drivers/hwmon/sbtsi_temp.c
+++ b/drivers/hwmon/sbtsi_temp.c
@@ -74,53 +74,52 @@ static int sbtsi_read(struct device *dev, enum hwmon_sensor_types type,
 		      u32 attr, int channel, long *val)
 {
 	struct sbtsi_data *data = dev_get_drvdata(dev);
+	u8 temp_int_reg, temp_dec_reg;
 	s32 temp_int, temp_dec;
 	int err;
 
 	switch (attr) {
 	case hwmon_temp_input:
-		/*
-		 * ReadOrder bit specifies the reading order of integer and
-		 * decimal part of CPU temp for atomic reads. If bit == 0,
-		 * reading integer part triggers latching of the decimal part,
-		 * so integer part should be read first. If bit == 1, read
-		 * order should be reversed.
-		 */
-		err = i2c_smbus_read_byte_data(data->client, SBTSI_REG_CONFIG);
-		if (err < 0)
-			return err;
-
-		mutex_lock(&data->lock);
-		if (err & BIT(SBTSI_CONFIG_READ_ORDER_SHIFT)) {
-			temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_DEC);
-			temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_INT);
-		} else {
-			temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_INT);
-			temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_DEC);
-		}
-		mutex_unlock(&data->lock);
+		temp_int_reg = SBTSI_REG_TEMP_INT;
+		temp_dec_reg = SBTSI_REG_TEMP_DEC;
 		break;
 	case hwmon_temp_max:
-		mutex_lock(&data->lock);
-		temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_HIGH_INT);
-		temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_HIGH_DEC);
-		mutex_unlock(&data->lock);
+		temp_int_reg = SBTSI_REG_TEMP_HIGH_INT;
+		temp_dec_reg = SBTSI_REG_TEMP_HIGH_DEC;
 		break;
 	case hwmon_temp_min:
-		mutex_lock(&data->lock);
-		temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_LOW_INT);
-		temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_LOW_DEC);
-		mutex_unlock(&data->lock);
+		temp_int_reg = SBTSI_REG_TEMP_LOW_INT;
+		temp_dec_reg = SBTSI_REG_TEMP_LOW_DEC;
 		break;
 	default:
 		return -EINVAL;
 	}
 
+	/*
+	 * ReadOrder bit specifies the reading order of integer and
+	 * decimal part of CPU temp for atomic reads. If bit == 0,
+	 * reading integer part triggers latching of the decimal part,
+	 * so integer part should be read first. If bit == 1, read
+	 * order should be reversed.
+	 */
+	err = i2c_smbus_read_byte_data(data->client, SBTSI_REG_CONFIG);
+	if (err < 0)
+		return err;
+
+	mutex_lock(&data->lock);
+	if (err & BIT(SBTSI_CONFIG_READ_ORDER_SHIFT)) {
+		temp_dec = i2c_smbus_read_byte_data(data->client, temp_dec_reg);
+		temp_int = i2c_smbus_read_byte_data(data->client, temp_int_reg);
+	} else {
+		temp_int = i2c_smbus_read_byte_data(data->client, temp_int_reg);
+		temp_dec = i2c_smbus_read_byte_data(data->client, temp_dec_reg);
+	}
+	mutex_unlock(&data->lock);
 
-	if (temp_int < 0)
-		return temp_int;
 	if (temp_dec < 0)
 		return temp_dec;
+	if (temp_int < 0)
+		return temp_int;
 
 	*val = sbtsi_reg_to_mc(temp_int, temp_dec);
 
-- 
2.17.1