[PATCH v2] hwmon: (sbtsi) Don't read sensor more than once if it doesn't respond

[Konstantin Aladyshev]

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 operation.

Signed-off-by: Konstantin Aladyshev <aladyshe...@gmail.com>
---
Changes in v2:
  - Fix typo in a commit message
  - Don't swap temp_int/temp_dec checks at the end of the 'sbtsi_read' function

 drivers/hwmon/sbtsi_temp.c | 55 +++++++++++++++++++-------------------
 1 file changed, 27 insertions(+), 28 deletions(-)

diff --git a/drivers/hwmon/sbtsi_temp.c b/drivers/hwmon/sbtsi_temp.c
index e35357c48b8e..4ae48635bb31 100644
--- a/drivers/hwmon/sbtsi_temp.c
+++ b/drivers/hwmon/sbtsi_temp.c
@@ -74,48 +74,47 @@ 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;
-- 
2.25.1