dt-bindings: pwm-stm32-lp: Add #pwm-cells

STM32 Low-Power Timer supports generic 3 cells PWM to encode PWM number,
period and polarity.

Signed-off-by: Gerald Baeza <gerald.baeza@st.com>
Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/pwm/pwm-stm32-lp.txt b/Documentation/devicetree/bindings/pwm/pwm-stm32-lp.txt
index f8338d11fd2b..bd23302e84be 100644
--- a/Documentation/devicetree/bindings/pwm/pwm-stm32-lp.txt
+++ b/Documentation/devicetree/bindings/pwm/pwm-stm32-lp.txt
@@ -7,6 +7,8 @@ See ../mfd/stm32-lptimer.txt for details about the parent node.
 
 Required parameters:
 - compatible:           Must be "st,stm32-pwm-lp".
+- #pwm-cells:           Should be set to 3. This PWM chip uses the default 3 cells
+                        bindings defined in pwm.txt.
 
 Optional properties:
 - pinctrl-names:        Set to "default".
@@ -18,6 +20,7 @@ Example:
                 ...
                 pwm {
                         compatible = "st,stm32-pwm-lp";
+                        #pwm-cells = <3>;
                         pinctrl-names = "default";
                         pinctrl-0 = <&lppwm1_pins>;
                 };