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

From: Konstantin Aladyshev
Date: Tue Apr 06 2021 - 14:17:23 EST


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 <aladyshev22@xxxxxxxxx>
---
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