pwm: add pca9685 driver

Add pwm driver for the NXP pca9685 16 channel pwm-led controller.

The driver is really barebones at this stage. E.g. the OE' pin and
therefore the corresponding registers are not supported.
The driver was tested on a HW where this pin is tied to GND.

Signed-off-by: Steffen Trumtrar <s.trumtrar@pengutronix.de>
[thierry.reding@gmail.com: style and whitespace cleanups]
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

1 files changed, 27 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/pwm/nxp,pca9685-pwm.txt b/Documentation/devicetree/bindings/pwm/nxp,pca9685-pwm.txt
new file mode 100644
index 000000000000..1e3dfe7a4894
--- /dev/null
+++ b/Documentation/devicetree/bindings/pwm/nxp,pca9685-pwm.txt
@@ -0,0 +1,27 @@
+NXP PCA9685 16-channel 12-bit PWM LED controller
+================================================
+
+Required properties:
+  - compatible: "nxp,pca9685-pwm"
+  - #pwm-cells: should be 2. The first cell specifies the per-chip index
+    of the PWM to use and the second cell is the period in nanoseconds.
+    The index 16 is the ALLCALL channel, that sets all PWM channels at the same
+    time.
+
+Optional properties:
+  - invert (bool): boolean to enable inverted logic
+  - open-drain (bool): boolean to configure outputs with open-drain structure;
+                       if omitted use totem-pole structure
+
+Example:
+
+For LEDs that are directly connected to the PCA, the following setting is
+applicable:
+
+pca: pca@41 {
+        compatible = "nxp,pca9685-pwm";
+        #pwm-cells = <2>;
+        reg = <0x41>;
+        invert;
+        open-drain;
+};