[PATCH 1/2] dt-bindings: pwm: clk-pwm: add optional GPIO and pinctrl properties

[Xilin Wu]

The clk-pwm driver cannot produce constant output levels (0% or 100%
duty cycle, or disabled state) through the clock hardware alone - the
actual pin level when the clock is off is undefined and
hardware-dependent.

Document optional gpios, pinctrl-names, pinctrl-0, and pinctrl-1
properties that allow the driver to switch the pin between clock
function mux (for normal PWM output) and GPIO mode (to drive a
deterministic constant level).

Signed-off-by: Xilin Wu <sophon@xxxxxxxxx>
---
 Documentation/devicetree/bindings/pwm/clk-pwm.yaml | 36 +++++++++++++++++++++-
 1 file changed, 35 insertions(+), 1 deletion(-)

diff --git a/Documentation/devicetree/bindings/pwm/clk-pwm.yaml b/Documentation/devicetree/bindings/pwm/clk-pwm.yaml
index ec1768291503..2a0e3e02d27b 100644
--- a/Documentation/devicetree/bindings/pwm/clk-pwm.yaml
+++ b/Documentation/devicetree/bindings/pwm/clk-pwm.yaml
@@ -15,6 +15,11 @@ description: |
   It's often possible to control duty-cycle of such clocks which makes them
   suitable for generating PWM signal.
 
+  Optionally, a GPIO and pinctrl states can be provided. When a constant
+  output level is needed (0%, 100%, or disabled), the pin is switched to
+  GPIO mode to drive the level directly. For normal PWM output the pin is
+  switched back to its clock function mux.
+
 allOf:
   - $ref: pwm.yaml#
 
@@ -29,6 +34,26 @@ properties:
   "#pwm-cells":
     const: 2
 
+  gpios:
+    description:
+      Optional GPIO used to drive a constant level when the PWM output is
+      disabled or set to 0% / 100% duty cycle. When provided, pinctrl states
+      "default" (clock mux) and "gpio" must also be defined.
+    maxItems: 1
+
+  pinctrl-names: true
+
+  pinctrl-0:
+    description: Pin configuration for clock function mux (normal PWM).
+    maxItems: 1
+
+  pinctrl-1:
+    description: Pin configuration for GPIO mode (constant level output).
+    maxItems: 1
+
+dependencies:
+  gpios: [ pinctrl-0, pinctrl-1 ]
+
 unevaluatedProperties: false
 
 required:
@@ -41,6 +66,15 @@ examples:
       compatible = "clk-pwm";
       #pwm-cells = <2>;
       clocks = <&gcc 0>;
-      pinctrl-names = "default";
+    };
+
+  - |
+    pwm {
+      compatible = "clk-pwm";
+      #pwm-cells = <2>;
+      clocks = <&gcc 0>;
+      pinctrl-names = "default", "gpio";
       pinctrl-0 = <&pwm_clk_flash_default>;
+      pinctrl-1 = <&pwm_clk_flash_gpio>;
+      gpios = <&tlmm 32 0>;
     };

-- 
2.53.0