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Subject[PATCH] hwmon: (sbtsi) Don't read sensor more than once if it doesn't respond
Date
From: Konstantin Aladyshev <aladyshev@nicevt.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@nicevt.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
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