hwmon: (pmbus/adm1275) Disable ADC while updating PMON_CONFIG

According to ADI, changing PMON_CONFIG while the ADC is running can have
unexpected results. ADI recommends halting the ADC with PMON_CONTROL
before setting PMON_CONFIG and then resume after. Follow ADI
recommendation and disable ADC while PMON_CONFIG is updated.

Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20230614163605.3688964-3-linux@roeck-us.net
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

Author: groeck

drivers/hwmon/pmbus/adm1275.c

@@ -27,8 +27,11 @@ enum chips { adm1075, adm1272, adm1275, adm1276, adm1278, adm1293, adm1294 };
 #define ADM1275_PEAK_IOUT		0xd0
 #define ADM1275_PEAK_VIN		0xd1
 #define ADM1275_PEAK_VOUT		0xd2
+#define ADM1275_PMON_CONTROL		0xd3
 #define ADM1275_PMON_CONFIG		0xd4
 
+#define ADM1275_CONVERT_EN		BIT(0)
+
 #define ADM1275_VIN_VOUT_SELECT		BIT(6)
 #define ADM1275_VRANGE			BIT(5)
 #define ADM1075_IRANGE_50		BIT(4)
@@ -202,7 +205,11 @@ static int adm1275_read_samples(const struct adm1275_data *data,
 static int adm1275_write_pmon_config(const struct adm1275_data *data,
 				     struct i2c_client *client, u16 word)
 {
-	int ret;
+	int ret, ret2;
+
+	ret = i2c_smbus_write_byte_data(client, ADM1275_PMON_CONTROL, 0);
+	if (ret)
+		return ret;
 
 	if (data->have_power_sampling)
 		ret = i2c_smbus_write_word_data(client, ADM1275_PMON_CONFIG,
@@ -211,6 +218,15 @@ static int adm1275_write_pmon_config(const struct adm1275_data *data,
 		ret = i2c_smbus_write_byte_data(client, ADM1275_PMON_CONFIG,
 						word);
 
+	/*
+	 * We still want to re-enable conversions if writing into
+	 * ADM1275_PMON_CONFIG failed.
+	 */
+	ret2 = i2c_smbus_write_byte_data(client, ADM1275_PMON_CONTROL,
+					 ADM1275_CONVERT_EN);
+	if (!ret)
+		ret = ret2;
+
 	return ret;
 }