On Tue, Feb 7, 2017 at 1:03 PM, Sylvain Lemieux <slemieux.tyco@xxxxxxxxx> wrote: > Hi Rob, > > On Tue, 2017-01-03 at 10:22 -0500, Sylvain Lemieux wrote: >> 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 >> > Can you provide feedback; I think your questions were answered > by Vladimir. Yes. Sorry for the delay. It's best to resend if you want to be sure I see it. Acked-by: Rob Herring <robh@xxxxxxxxxx> Rob -- 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
