iio: mlx90614: Add power management

Add support for system sleep and runtime power management.

To wake up the device, the SDA line should be held low for at least 33ms
while SCL is high.  As this is not possible using the i2c API (and not
supported by all i2c adapters), a GPIO connected to the SDA line is
needed.  The GPIO is named "wakeup" and can be specified in a device
tree with the "wakeup-gpios" binding.

If the wake-up GPIO is not given, disable power management for the
device.  Entering sleep requires an SMBus byte access, hence power
management is also disabled if byte access is not supported by the
adapter.

Signed-off-by: Vianney le Clément de Saint-Marcq <vianney.leclement@essensium.com>
Cc: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

1 files changed, 9 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/iio/temperature/mlx90614.txt b/Documentation/devicetree/bindings/iio/temperature/mlx90614.txt
index 4c959f3b8663..9be57b036092 100644
--- a/Documentation/devicetree/bindings/iio/temperature/mlx90614.txt
+++ b/Documentation/devicetree/bindings/iio/temperature/mlx90614.txt
@@ -7,9 +7,18 @@ Required properties:
   - compatible: should be "melexis,mlx90614"
   - reg: the I2C address of the sensor
 
+Optional properties:
+
+  - wakeup-gpios: device tree identifier of the GPIO connected to the SDA line
+      to hold low in order to wake up the device.  In normal operation, the
+      GPIO is set as input and will not interfere in I2C communication.  There
+      is no need for a GPIO driving the SCL line.  If no GPIO is given, power
+      management is disabled.
+
 Example:
 
 mlx90614@5a {
 	compatible = "melexis,mlx90614";
 	reg = <0x5a>;
+	wakeup-gpios = <&gpio0 2 GPIO_ACTIVE_HIGH>;
 };