iio: light: cm32181: Add PM support

The read on in_illuminance_input keeps at 0 after system sleep.

So add proper suspend and resume callback to make the sensor keep
working after system sleep.

Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
Link: https://lore.kernel.org/r/20220707000151.33381-1-kai.heng.feng@canonical.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/light/cm32181.c

@@ -460,6 +460,8 @@ static int cm32181_probe(struct i2c_client *client)
 			return PTR_ERR(client);
 	}
 
+	i2c_set_clientdata(client, indio_dev);
+
 	cm32181 = iio_priv(indio_dev);
 	cm32181->client = client;
 	cm32181->dev = dev;
@@ -486,6 +488,25 @@ static int cm32181_probe(struct i2c_client *client)
 	return 0;
 }
 
+static int cm32181_suspend(struct device *dev)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+
+	return i2c_smbus_write_word_data(client, CM32181_REG_ADDR_CMD,
+					 CM32181_CMD_ALS_DISABLE);
+}
+
+static int cm32181_resume(struct device *dev)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct cm32181_chip *cm32181 = iio_priv(dev_get_drvdata(dev));
+
+	return i2c_smbus_write_word_data(client, CM32181_REG_ADDR_CMD,
+					 cm32181->conf_regs[CM32181_REG_ADDR_CMD]);
+}
+
+DEFINE_SIMPLE_DEV_PM_OPS(cm32181_pm_ops, cm32181_suspend, cm32181_resume);
+
 static const struct of_device_id cm32181_of_match[] = {
 	{ .compatible = "capella,cm3218" },
 	{ .compatible = "capella,cm32181" },
@@ -506,6 +527,7 @@ static struct i2c_driver cm32181_driver = {
 		.name	= "cm32181",
 		.acpi_match_table = ACPI_PTR(cm32181_acpi_match),
 		.of_match_table = cm32181_of_match,
+		.pm = pm_sleep_ptr(&cm32181_pm_ops),
 	},
 	.probe_new	= cm32181_probe,
 };