From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rob Herring Subject: Re: [PATCH v2 11/16] pwm: add documentation for PWM modes Date: Fri, 19 Jan 2018 16:39:08 -0600 Message-ID: <20180119223908.b3dxdx53nzuhakzw@rob-hp-laptop> References: <1515766983-15151-1-git-send-email-claudiu.beznea@microchip.com> <1515766983-15151-12-git-send-email-claudiu.beznea@microchip.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1515766983-15151-12-git-send-email-claudiu.beznea@microchip.com> Sender: linux-pwm-owner@vger.kernel.org To: Claudiu Beznea Cc: thierry.reding@gmail.com, mark.rutland@arm.com, linux@armlinux.org.uk, daniel@zonque.org, haojian.zhuang@gmail.com, robert.jarzmik@free.fr, corbet@lwn.net, nicolas.ferre@microchip.com, alexandre.belloni@free-electrons.com, linux-pwm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-amlogic@lists.infradead.org, linux-rockchip@lists.infradead.org, linux-rpi-kernel@lists.infradead.org, devicetree@vger.kernel.org List-Id: devicetree@vger.kernel.org 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 > --- > 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 > -) in a third cell: > +Optionally, the pwm-specifier can encode: > +1. a number of flags (defined in ) 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 ) 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 >