[v3,06/10] pwm: add PWM modes

Message ID 1519300881-8136-7-git-send-email-claudiu.beznea@microchip.com
State Changes Requested
Headers show
Series
  • extend PWM framework to support PWM modes
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Commit Message

Claudiu Beznea Feb. 22, 2018, 12:01 p.m.
Add PWM normal and complementary modes.

Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
---
 Documentation/devicetree/bindings/pwm/pwm.txt |  9 +++++++--
 Documentation/pwm.txt                         | 26 +++++++++++++++++++++++---
 include/dt-bindings/pwm/pwm.h                 |  1 +
 3 files changed, 31 insertions(+), 5 deletions(-)

Comments

Andy Shevchenko Feb. 22, 2018, 5:28 p.m. | #1
On Thu, Feb 22, 2018 at 2:01 PM, Claudiu Beznea
<claudiu.beznea@microchip.com> wrote:
> Add PWM normal and complementary modes.

> +- PWM_DTMODE_COMPLEMENTARY: PWM complementary working mode (for PWM
> +channels two outputs); if not specified, the default for PWM channel will
> +be used

What DT stands for?
Claudiu Beznea Feb. 22, 2018, 5:42 p.m. | #2
On 22.02.2018 19:28, Andy Shevchenko wrote:
> On Thu, Feb 22, 2018 at 2:01 PM, Claudiu Beznea
> <claudiu.beznea@microchip.com> wrote:
>> Add PWM normal and complementary modes.
> 
>> +- PWM_DTMODE_COMPLEMENTARY: PWM complementary working mode (for PWM
>> +channels two outputs); if not specified, the default for PWM channel will
>> +be used
> 
> What DT stands for?
It stands for Device Tree. It remained this way from the previous version. In
the previous version I had modes described in an enum, to be used by PWM core,
as follows:
enum pwm_mode {
	PWM_MODE_NORMAL,
	PWM_MODE_COMPLEMENTARY,
};

and, to avoid conflict b/w these defines and the one from
include/dt-bindings/pwm/pwm.h I introduced this DT in the define names from
dt-bindings. But now the DT might be removed since I've changed the way the PWM
mode is identified in PWM core. I will remove the DT in the next version, if not
requested otherwise.

Thank you,
Claudiu Benea
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Patch

diff --git a/Documentation/devicetree/bindings/pwm/pwm.txt b/Documentation/devicetree/bindings/pwm/pwm.txt
index 8556263b8502..c2b4b9ba0e3f 100644
--- a/Documentation/devicetree/bindings/pwm/pwm.txt
+++ b/Documentation/devicetree/bindings/pwm/pwm.txt
@@ -46,11 +46,16 @@  period in nanoseconds.
 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
+- PWM_DTMODE_COMPLEMENTARY: PWM complementary working mode (for PWM
+channels two outputs); if not specified, the default for PWM channel will
+be used
 
-Example with optional PWM specifier for inverse polarity
+Example with optional PWM specifier for inverse polarity and complementary
+mode:
 
 	bl: backlight {
-		pwms = <&pwm 0 5000000 PWM_POLARITY_INVERTED>;
+		pwms = <&pwm 0 5000000
+			(PWM_DTMODE_COMPLEMENTARY | PWM_POLARITY_INVERTED)>;
 		pwm-names = "backlight";
 	};
 
diff --git a/Documentation/pwm.txt b/Documentation/pwm.txt
index 8fbf0aa3ba2d..59592f8cc381 100644
--- a/Documentation/pwm.txt
+++ b/Documentation/pwm.txt
@@ -61,9 +61,9 @@  In addition to the PWM state, the PWM API also exposes PWM arguments, which
 are the reference PWM config one should use on this PWM.
 PWM arguments are usually platform-specific and allows the PWM user to only
 care about dutycycle relatively to the full period (like, duty = 50% of the
-period). struct pwm_args contains 2 fields (period and polarity) and should
-be used to set the initial PWM config (usually done in the probe function
-of the PWM user). PWM arguments are retrieved with pwm_get_args().
+period). struct pwm_args contains 3 fields (period, polarity and mode) and
+should be used to set the initial PWM config (usually done in the probe
+function of the PWM user). PWM arguments are retrieved with pwm_get_args().
 
 Using PWMs with the sysfs interface
 -----------------------------------
@@ -110,6 +110,26 @@  channel that was exported. The following properties will then be available:
 	- 0 - disabled
 	- 1 - enabled
 
+  mode
+    Get/set PWM channel working mode.
+
+    Normal mode - for PWM channels with one output; this should be the
+        default working mode for every PWM channel; output waveforms looks
+        like this:
+             __    __    __    __
+    PWM   __|  |__|  |__|  |__|  |__
+            <--T-->
+
+    Complementary mode - for PWM channels two outputs; output waveforms
+        looks line this:
+             __    __    __    __
+    PWMH1 __|  |__|  |__|  |__|  |__
+          __    __    __    __    __
+    PWML1   |__|  |__|  |__|  |__|
+            <--T-->
+
+    Where T is the signal period.
+
 Implementing a PWM driver
 -------------------------
 
diff --git a/include/dt-bindings/pwm/pwm.h b/include/dt-bindings/pwm/pwm.h
index ab9a077e3c7d..b4d61269aced 100644
--- a/include/dt-bindings/pwm/pwm.h
+++ b/include/dt-bindings/pwm/pwm.h
@@ -11,5 +11,6 @@ 
 #define _DT_BINDINGS_PWM_PWM_H
 
 #define PWM_POLARITY_INVERTED			(1 << 0)
+#define PWM_DTMODE_COMPLEMENTARY		(1 << 1)
 
 #endif