[PATCH v2 2/7] hwmon: (nct6683) Restore automatic fan control on driver removal

[Johan Dahlin <jdahlin@gmail.com>]

A fan switched to manual mode through pwmN_enable keeps its last duty
cycle after the driver is unloaded, with nothing left to adjust it.

Return the channels the driver switched to manual mode to automatic mode
when the device is removed, using the bitmap kept for resume. Other
channels are not touched.

Signed-off-by: Johan Dahlin <jdahlin@gmail.com>
---
 drivers/hwmon/nct6683.c | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/drivers/hwmon/nct6683.c b/drivers/hwmon/nct6683.c
index 0565ca9290eb..d43dcf90048b 100644
--- a/drivers/hwmon/nct6683.c
+++ b/drivers/hwmon/nct6683.c
@@ -1584,6 +1584,32 @@ static void nct6683_setup_sensors(struct nct6683_data *data)
 	}
 }
 
+/*
+ * Hand the fans the driver switched to manual mode back to the EC, so that
+ * they do not stay at a fixed duty cycle once nobody is left to adjust it.
+ */
+static void nct6683_restore_fan_control(void *_dev)
+{
+	struct device *dev = _dev;
+	struct nct6683_data *data = dev_get_drvdata(dev);
+	unsigned long manual;
+	int ch, err;
+
+	mutex_lock(&data->update_lock);
+	manual = data->pwm_manual;
+	for_each_set_bit(ch, &manual, NCT6683_NUM_REG_FAN) {
+		err = nct6683_fan_ctrl_update(data, ch, false, -1);
+		if (err) {
+			dev_warn(dev, "Failed to restore automatic mode of pwm%d: %d\n",
+				 ch + 1, err);
+			/* The EC does not respond, skip the remaining channels */
+			if (err == -ETIMEDOUT)
+				break;
+		}
+	}
+	mutex_unlock(&data->update_lock);
+}
+
 static int nct6683_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
@@ -1593,6 +1619,7 @@ static int nct6683_probe(struct platform_device *pdev)
 	struct device *hwmon_dev;
 	struct resource *res;
 	int groups = 0;
+	int err;
 	char build[16];
 
 	res = platform_get_resource(pdev, IORESOURCE_IO, 0);
@@ -1710,6 +1737,13 @@ static int nct6683_probe(struct platform_device *pdev)
 		 nct6683_read(data, NCT6683_REG_VERSION_LO),
 		 build);
 
+	if (data->have_fan_ctrl) {
+		err = devm_add_action_or_reset(dev, nct6683_restore_fan_control,
+					       dev);
+		if (err)
+			return err;
+	}
+
 	hwmon_dev = devm_hwmon_device_register_with_groups(dev,
 			nct6683_device_names[data->kind], data, data->groups);
 	return PTR_ERR_OR_ZERO(hwmon_dev);
-- 
2.53.0