[v2,15/16] pwm: add documentation for pwm push-pull mode

Commit Message

Claudiu Beznea Jan. 12, 2018, 2:23 p.m. UTC

Add documentation for PWM push-pull mode.

Signed-off-by: Claudiu Beznea <[e-mail]>
---
 Documentation/devicetree/bindings/pwm/pwm.txt |  8 +++++++-
 Documentation/pwm.txt                         | 18 ++++++++++++++++++
 2 files changed, 25 insertions(+), 1 deletion(-)

Comments

Rob Herring (Arm) Jan. 19, 2018, 10:41 p.m. UTC | #1

On Fri, Jan 12, 2018 at 04:23:02PM +0200, Claudiu Beznea wrote:
> Add documentation for PWM push-pull mode.
> 
> Signed-off-by: Claudiu Beznea <[e-mail]>
> ---
>  Documentation/devicetree/bindings/pwm/pwm.txt |  8 +++++++-
>  Documentation/pwm.txt                         | 18 ++++++++++++++++++
>  2 files changed, 25 insertions(+), 1 deletion(-)

Other than squashing the previous patch into this one,

Reviewed-by: Rob Herring <[e-mail]>

Patch

diff --git a/Documentation/devicetree/bindings/pwm/pwm.txt b/Documentation/devicetree/bindings/pwm/pwm.txt
index fdff25bad1db..a4562af3577c 100644
--- a/Documentation/devicetree/bindings/pwm/pwm.txt
+++ b/Documentation/devicetree/bindings/pwm/pwm.txt
@@ -58,15 +58,21 @@  Example with optional PWM specifier for inverse polarity
 - PWM_MODE_NORMAL: for all PWM controllers
 - PWM_MODE_COMPLEMENTARY: for PWM controllers with more than one output per
 PWM channel
+- PWM_MODE_PUSH_PULL: for PWM controllers with more than one output per channel,
+in push-pull mode
 
 Example with PWM modes:
 
 	bl: blacklight {
 		pwms = <&pwm 0 5000000 PWM_POLARITY_INVERTED
-			PWM_DTMODE_NORMAL | PWM_DTMODE_COMPLEMENTARY>;
+			PWM_DTMODE_NORMAL | PWM_DTMODE_COMPLEMENTARY |
+			PWM_DTMODE_PUSH_PULL>;
 		pwm-names = "backlight";
 	};
 
+If all the available modes are given as argument of pwms binding only the first
+valid one will be considered (first valid LSB bit of mode field).
+
 2) PWM controller nodes
 -----------------------
 
diff --git a/Documentation/pwm.txt b/Documentation/pwm.txt
index 58c9bd55f021..71b538239519 100644
--- a/Documentation/pwm.txt
+++ b/Documentation/pwm.txt
@@ -135,6 +135,24 @@  channel that was exported. The following properties will then be available:
 
     Where T is the signal period.
 
+    Push-pull mode - for PWM chips with mode than one output per PWM channel;
+        output waveform for a PWM controller with 2 outputs per PWM channel, in
+	push-pull mode, with normal polarity looks like this:
+            __          __
+    PWMH __|  |________|  |________
+                  __          __
+    PWML ________|  |________|  |__
+           <--T-->
+
+    If polarity is inversed:
+         __    ________    ________
+    PWMH   |__|        |__|
+         ________    ________    __
+    PWML         |__|        |__|
+           <--T-->
+
+    Where T is the signal period.
+
 Implementing a PWM driver
 -------------------------