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SubjectRe: [PATCH v2 11/16] pwm: add documentation for PWM modes
On Fri, Jan 12, 2018 at 04:22:58PM +0200, Claudiu Beznea wrote:
> Add documentation for PWM normal and complementary modes.

This and the previous patch can be combined.

>
> Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
> ---
> Documentation/devicetree/bindings/pwm/pwm.txt | 17 ++++++++++++++--
> Documentation/pwm.txt | 29 +++++++++++++++++++++++++--
> 2 files changed, 42 insertions(+), 4 deletions(-)
>
> diff --git a/Documentation/devicetree/bindings/pwm/pwm.txt b/Documentation/devicetree/bindings/pwm/pwm.txt
> index 8556263b8502..fdff25bad1db 100644
> --- a/Documentation/devicetree/bindings/pwm/pwm.txt
> +++ b/Documentation/devicetree/bindings/pwm/pwm.txt
> @@ -43,8 +43,8 @@ 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 (defined in
> -<dt-bindings/pwm/pwm.h>) in a third cell:
> +Optionally, the pwm-specifier can encode:
> +1. a number of flags (defined in <dt-bindings/pwm/pwm.h>) in a third cell:

Based on the prior patches, "third cell" is probably to restrictive
here and it should just say "in a flags cell".

> - PWM_POLARITY_INVERTED: invert the PWM signal polarity
>
> Example with optional PWM specifier for inverse polarity
> @@ -54,6 +54,19 @@ Example with optional PWM specifier for inverse polarity
> pwm-names = "backlight";
> };
>
> +2. PWM working modes (defined in <dt-bindings/pwm/pwm.h>) in the 4th cell:
> +- PWM_MODE_NORMAL: for all PWM controllers
> +- PWM_MODE_COMPLEMENTARY: for PWM controllers with more than one output per
> +PWM channel
> +
> +Example with PWM modes:
> +
> + bl: blacklight {
> + pwms = <&pwm 0 5000000 PWM_POLARITY_INVERTED
> + PWM_DTMODE_NORMAL | PWM_DTMODE_COMPLEMENTARY>;
> + pwm-names = "backlight";
> + };
> +
> 2) PWM controller nodes
> -----------------------
>
> diff --git a/Documentation/pwm.txt b/Documentation/pwm.txt
> index 8fbf0aa3ba2d..58c9bd55f021 100644
> --- a/Documentation/pwm.txt
> +++ b/Documentation/pwm.txt
> @@ -61,8 +61,8 @@ 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
> +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
> @@ -83,6 +83,9 @@ will find:
> unexport
> Unexports a PWM channel from sysfs (write-only).
>
> + mode
> + PWM chip supported modes.
> +
> The PWM channels are numbered using a per-chip index from 0 to npwm-1.
>
> When a PWM channel is exported a pwmX directory will be created in the
> @@ -110,6 +113,28 @@ channel that was exported. The following properties will then be available:
> - 0 - disabled
> - 1 - enabled
>
> + mode
> + Set PWM channel working mode (normal and complementary). PWM chip with
> + complementary mode could also work in normal mode by using only one physical
> + output.
> +
> + Normal mode - for PWM chips with one output per PWM channel; output
> + waveforms looks like this:
> + __ __ __ __
> + PWM __| |__| |__| |__| |__
> + <--T-->
> +
> + Complementary mode - for PWM chips with more than one output per PWM
> + channel; output waveforms for a PWM controller with 2 outputs per PWM
> + channel looks line this:
> + __ __ __ __
> + PWMH1 __| |__| |__| |__| |__
> + __ __ __ __ __
> + PWML1 |__| |__| |__| |__|
> + <--T-->
> +
> + Where T is the signal period.
> +
> Implementing a PWM driver
> -------------------------
>
> --
> 2.7.4
>

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