Hi Rob, On Wed, 2016-12-21 at 05:30 +0200, Vladimir Zapolskiy wrote: > On 12/10/2016 01:51 AM, Vladimir Zapolskiy wrote: > > Hi Rob, > > > > On 12/09/2016 11:41 PM, Rob Herring wrote: > >> On Mon, Dec 05, 2016 at 03:42:37AM +0200, Vladimir Zapolskiy wrote: > >>> NXP LPC32xx SoCs have two simple independent PWM controllers with a single > >>> output each, in this case there is no need to specify PWM channel argument > >>> on client side, one cell for setting PWM output frequency is sufficient. > >>> > >>> Another added to the description property 'clocks' has a standard meaning > >>> of a controller supply clock, in the LPC32xx User's Manual the clock is > >>> denoted as PWM1_CLK or PWM2_CLK clock. > >>> > >>> Signed-off-by: Vladimir Zapolskiy <vz@xxxxxxxxx> > >>> --- > >>> Documentation/devicetree/bindings/pwm/lpc32xx-pwm.txt | 7 +++++++ > >>> 1 file changed, 7 insertions(+) > >>> > >>> diff --git a/Documentation/devicetree/bindings/pwm/lpc32xx-pwm.txt b/Documentation/devicetree/bindings/pwm/lpc32xx-pwm.txt > >>> index 74b5bc5..523d796 100644 > >>> --- a/Documentation/devicetree/bindings/pwm/lpc32xx-pwm.txt > >>> +++ b/Documentation/devicetree/bindings/pwm/lpc32xx-pwm.txt > >>> @@ -3,15 +3,22 @@ LPC32XX PWM controller > >>> Required properties: > >>> - compatible: should be "nxp,lpc3220-pwm" > >>> - reg: physical base address and length of the controller's registers > >>> +- clocks: clock phandle and clock specifier pair > >>> +- #pwm-cells: should be 1, the cell is used to specify the period in > >>> + nanoseconds. > >> > >> This use of the cell is a bit odd as the period is s/w config and this > >> would typically be a channel selection or such. > > > > this is a classic PWM channel configuration property for PWM consumers > > described in DT, for instance PWM frequency for display panel backlight > > on boot. > > > > I think >90% of PWM controllers with device tree bindings have this > > argument in #pwm-cells, from bindings/pwm/pwm.txt : > > > > pwm-specifier typically encodes the chip-relative PWM number and > > the PWM period in nanoseconds. > > > > You also may skim through phandle arguments of 'pwms' property, > > commonly the second argument is the requested frequency. > > > > In this particular case I just drop PWM channel number, because > > the LPC32xx PWM controller has a single output channel. > > > >> What if I want user specified/changed periods? > >> > > > > The preset period still can be changed over sysfs in runtime. > > Rob, have I managed to answer your questions? > > If you accept my clarification, could you please ack the change? > > -- > With best wishes, > Vladimir > ping Sylvain -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
