pwm: Add PWM polarity flag macro for DT

Define a PWM_POLARITY_INVERTED macro in include/dt-bindings/pwm/pwm.h to
be used by device tree sources.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

2 files changed, 18 insertions, 3 deletions

diff --git a/Documentation/devicetree/bindings/pwm/pwm.txt b/Documentation/devicetree/bindings/pwm/pwm.txt
index 06e67247859a..8556263b8502 100644
--- a/Documentation/devicetree/bindings/pwm/pwm.txt
+++ b/Documentation/devicetree/bindings/pwm/pwm.txt
@@ -43,13 +43,14 @@ because the name "backlight" would be used as fallback anyway.
 pwm-specifier typically encodes the chip-relative PWM number and the PWM
 period in nanoseconds.
 
-Optionally, the pwm-specifier can encode a number of flags in a third cell:
-- bit 0: PWM signal polarity (0: normal polarity, 1: inverse polarity)
+Optionally, the pwm-specifier can encode a number of flags (defined in
+<dt-bindings/pwm/pwm.h>) in a third cell:
+- PWM_POLARITY_INVERTED: invert the PWM signal polarity
 
 Example with optional PWM specifier for inverse polarity
 
         bl: backlight {
-                pwms = <&pwm 0 5000000 1>;
+                pwms = <&pwm 0 5000000 PWM_POLARITY_INVERTED>;
                 pwm-names = "backlight";
         };
 
diff --git a/include/dt-bindings/pwm/pwm.h b/include/dt-bindings/pwm/pwm.h
new file mode 100644
index 000000000000..96f49e82253e
--- /dev/null
+++ b/include/dt-bindings/pwm/pwm.h
@@ -0,0 +1,14 @@
+/*
+ * This header provides constants for most PWM bindings.
+ *
+ * Most PWM bindings can include a flags cell as part of the PWM specifier.
+ * In most cases, the format of the flags cell uses the standard values
+ * defined in this header.
+ */
+
+#ifndef _DT_BINDINGS_PWM_PWM_H
+#define _DT_BINDINGS_PWM_PWM_H
+
+#define PWM_POLARITY_INVERTED                   (1 << 0)
+
+#endif