Subject: [PATCH v4 2/4] pwm: sirf: add dt-binding document

From: [email-masked] (Thierry Reding)
Date: Tue, 18 Mar 2014 22:13:40 +0100

On Wed, Mar 05, 2014 at 05:59:43PM +0800, Barry Song wrote:
> From: Barry Song <[email-masked]>
> 
> this patch adds dt-binding document for pwm-sirf. here the controller clock
> can't generate PWM signals, so we need seperate clock as signal source.

Please capitalize properly. Also since the binding document should be OS
agnostic, it shouldn't be using the name of the driver in the Linux
kernel.

> diff --git a/Documentation/devicetree/bindings/pwm/pwm-sirf.txt b/Documentation/devicetree/bindings/pwm/pwm-sirf.txt
> new file mode 100644
> index 0000000..47851ea
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/pwm/pwm-sirf.txt
> @@ -0,0 +1,23 @@
> +SiRF prima2 & atlas6 PWM drivers
> +
> +Required properties:
> +- compatible: "sirf,prima2-pwm"
> +- reg: physical base address and length of the controller's registers
> +- #pwm-cells: should be 2.  The first cell specifies the per-chip index of the
> +  PWM to use and the second cell is the period in nanoseconds.

The canonical way to describe this property is:

	- #pwm-cells: Should be 2. See pwm.txt in this directory for a description of
	  the cells format.

> +- clocks: from common clock binding: the 1st clock is for PWM controller the
> +  other clocks are the sources to generate PWM signals
> +- clock-names : The first one is the name of the clock for PWM, others are names
> +  of clock sources to generate PWM signal, e.g.sigsrc0 ~sigsrc4. For prima2 and
> +  atlas6, sigsrc0 is OSC with 26MHz, sigsrc3 is RTC with 32KHz, others are PLLs.
> +  Generally, PWM module uses the OSC as clock source to generate PWM signals.

I think a more common way to write this is:

	- clocks: Must contain an entry for each entry in clock-names.
	  See ../clocks/clock-bindings.txt for details.
	- clock-names: Must include the following entries:
	  - pwmc: PWM controller clock
	  - sigsrc0: source clock for ???
	  - ...
	  - sigsrc4: source clock for ???

And perhaps given the requirements on prima2 and atlas6 (are those SoC
generations or boards?) specify what each clock should be set to.

If prima2 and atlas6 are boards, then the binding shouldn't mention them
at all.

Thierry
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