[PATCH] hwmon: (spd5118) Explicitly enable temperature sensor in probe function

[Guenter Roeck <linux@roeck-us.net>]

Instantiating the driver does not make sense if the temperature sensor
is disabled, so enable it unconditionally in the probe function.

If that fails, write operations to the chip are likely disabled
by the I2C controller. Bail out with an error message if that happens.

Cc: Armin Wolf <W_Armin@gmx.de>
Cc: Kurt Borja <kuurtb@gmail.com>
Cc: Tinsae Tadesse <tinsaetadesse2015@gmail.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
 drivers/hwmon/spd5118.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/hwmon/spd5118.c b/drivers/hwmon/spd5118.c
index 5da44571b6a0..d8834d4d980b 100644
--- a/drivers/hwmon/spd5118.c
+++ b/drivers/hwmon/spd5118.c
@@ -552,6 +552,20 @@ static int spd5118_common_probe(struct device *dev, struct regmap *regmap,
 	if (!spd5118_vendor_valid(bank, vendor))
 		return -ENODEV;
 
+	/*
+	 * Some I2C controllers write protect the address range used by SPD5118
+	 * compliant chips. This makes the chips effectively unaccessible since
+	 * the driver needs to be able to set the page in the legacy mode
+	 * register, and it needs to be able to disable the temperature sensor
+	 * during suspend. Check if writes to the chip are possible by
+	 * explicitly enabling the temperature sensor. Bail out if that fails.
+	 */
+	err = regmap_write_bits(regmap, SPD5118_REG_TEMP_CONFIG,
+				SPD5118_TS_DISABLE, 0);
+	if (err)
+		return dev_err_probe(dev, err,
+				     "Failed to enable temperature sensor (write protected ?)\n");
+
 	data->regmap = regmap;
 	mutex_init(&data->nvmem_lock);
 	dev_set_drvdata(dev, data);
-- 
2.45.2