[PATCH 1/3] dt: pwm: lpc32xx: add description of clocks and #pwm-cells properties

[Rob Herring]

On Tue, Feb 7, 2017 at 1:03 PM, Sylvain Lemieux <slemieux.tyco at gmail.com> 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 at mleia.com>
>> > >>> ---
>> > >>>  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 at kernel.org>

Rob