[v3,06/10] pwm: add PWM modes
Commit Message
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
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?
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
@@ -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";
};
@@ -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
-------------------------
@@ -11,5 +11,6 @@
#define _DT_BINDINGS_PWM_PWM_H
#define PWM_POLARITY_INVERTED (1 << 0)
+#define PWM_DTMODE_COMPLEMENTARY (1 << 1)
#endif