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SubjectRe: [PATCH v2 11/16] pwm: add documentation for PWM modes
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On 20.01.2018 00:39, Rob Herring wrote:
> 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.
OK
>
>>
>> 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".
OK

Thank you,
Claudiu Beznea
>
>> - 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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