[PATCH] iio: light: veml6040: add suspend/resume support

[Stepan Ionichev <sozdayvek@gmail.com>]

The VEML6040 RGBW light sensor stays in auto-measurement mode at all
times once probed, drawing its full active current (~200 uA per
Vishay VEML6040 datasheet, Doc# 84276 Rev. 1.7). On system suspend
there is no need to keep the sensor running.

Add system sleep PM callbacks that toggle the SD (shutdown) bit in
CONF register 00H to put the chip into shutdown on suspend and back
into normal operation on resume. The bit semantics are documented in
the datasheet Tables 2-1 and 2-2.

The existing veml6040_shutdown_action() is unchanged; it still runs
on module unload to leave the chip shut down.

Signed-off-by: Stepan Ionichev <sozdayvek@gmail.com>
---
 drivers/iio/light/veml6040.c | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/drivers/iio/light/veml6040.c b/drivers/iio/light/veml6040.c
index f563f9f0e..ffd0a2a70 100644
--- a/drivers/iio/light/veml6040.c
+++ b/drivers/iio/light/veml6040.c
@@ -13,6 +13,7 @@
 #include <linux/iio/iio.h>
 #include <linux/iio/sysfs.h>
 #include <linux/module.h>
+#include <linux/pm.h>
 #include <linux/regmap.h>
 
 /* VEML6040 Configuration Registers
@@ -201,6 +202,32 @@ static void veml6040_shutdown_action(void *data)
 			   VEML6040_CONF_SD_MSK, VEML6040_CONF_SD_MSK);
 }
 
+/*
+ * Per Vishay VEML6040 datasheet (Doc# 84276 Rev. 1.7), Table 2-1 and
+ * Table 2-2, the SD bit in CONF register 00H controls chip shutdown:
+ * SD = 1 disables the color sensor, SD = 0 re-enables it.
+ */
+static int veml6040_suspend(struct device *dev)
+{
+	struct iio_dev *indio_dev = i2c_get_clientdata(to_i2c_client(dev));
+	struct veml6040_data *data = iio_priv(indio_dev);
+
+	return regmap_update_bits(data->regmap, VEML6040_CONF_REG,
+				  VEML6040_CONF_SD_MSK, VEML6040_CONF_SD_MSK);
+}
+
+static int veml6040_resume(struct device *dev)
+{
+	struct iio_dev *indio_dev = i2c_get_clientdata(to_i2c_client(dev));
+	struct veml6040_data *data = iio_priv(indio_dev);
+
+	return regmap_update_bits(data->regmap, VEML6040_CONF_REG,
+				  VEML6040_CONF_SD_MSK, 0);
+}
+
+static DEFINE_SIMPLE_DEV_PM_OPS(veml6040_pm_ops, veml6040_suspend,
+				veml6040_resume);
+
 static int veml6040_probe(struct i2c_client *client)
 {
 	struct device *dev = &client->dev;
@@ -271,6 +298,7 @@ static struct i2c_driver veml6040_driver = {
 	.driver = {
 		.name = "veml6040",
 		.of_match_table = veml6040_of_match,
+		.pm = pm_sleep_ptr(&veml6040_pm_ops),
 	},
 };
 module_i2c_driver(veml6040_driver);
-- 
2.43.0