linux-kernel - Re: [PATCH 1/7] add binding for stm32 multifunctions timer driver

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Date:   Tue, 22 Nov 2016 16:52:28 +0000
From:   Lee Jones <lee.jones@...aro.org>
To:     Benjamin Gaignard <benjamin.gaignard@...aro.org>
Cc:     robh+dt@...nel.org, mark.rutland@....com, alexandre.torgue@...com,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        thierry.reding@...il.com, linux-pwm@...r.kernel.org,
        jic23@...nel.org, knaack.h@....de, lars@...afoo.de,
        pmeerw@...erw.net, linux-iio@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, fabrice.gasnier@...com,
        gerald.baeza@...com, arnaud.pouliquen@...com,
        linus.walleij@...aro.org, linaro-kernel@...ts.linaro.org,
        Benjamin Gaignard <benjamin.gaignard@...com>
Subject: Re: [PATCH 1/7] add binding for stm32 multifunctions timer driver

On Tue, 22 Nov 2016, Benjamin Gaignard wrote:

> Add bindings information for stm32 timer MFD
> 
> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@...com>
> ---
>  .../devicetree/bindings/mfd/stm32-timer.txt        | 53 ++++++++++++++++++++++
>  1 file changed, 53 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/mfd/stm32-timer.txt
> 
> diff --git a/Documentation/devicetree/bindings/mfd/stm32-timer.txt b/Documentation/devicetree/bindings/mfd/stm32-timer.txt
> new file mode 100644
> index 0000000..3cefce1
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/mfd/stm32-timer.txt
> @@ -0,0 +1,53 @@
> +STM32 multifunctions timer driver

"STM32 Multi-Function Timer/PWM device bindings"

Doesn't this shared device have a better name?

> +stm32 timer MFD allow to handle at the same time pwm and IIO timer devices

No need for this sentence.

> +Required parameters:
> +- compatible: must be one of the follow value:
> +	"st,stm32-mfd-timer1"
> +	"st,stm32-mfd-timer2"
> +	"st,stm32-mfd-timer3"
> +	"st,stm32-mfd-timer4"
> +	"st,stm32-mfd-timer5"
> +	"st,stm32-mfd-timer6"
> +	"st,stm32-mfd-timer7"
> +	"st,stm32-mfd-timer8"
> +	"st,stm32-mfd-timer9"
> +	"st,stm32-mfd-timer10"
> +	"st,stm32-mfd-timer11"
> +	"st,stm32-mfd-timer12"
> +	"st,stm32-mfd-timer13"
> +	"st,stm32-mfd-timer14"

We don't normally number devices.

What's stopping you from simply doing:

	pwm1: pwm1@...10000 {
		compatible = "st,stm32-pwm";
	};
	pwm2: pwm1@...20000 {
		compatible = "st,stm32-pwm";
	};
	pwm3: pwm1@...30000 {
		compatible = "st,stm32-pwm";
	};

> +- reg :			Physical base address and length of the controller's
> +			registers.
> +- clock-names: 		Set to "mfd_timer_clk".

How many clocks are there?

If only 1, you don't need this property.

"mfd_timer_clk" is not the correct name.

What is it called in the datasheet?

> +- clocks: 		Phandle of the clock used by the timer module.

"Phandle to the clock ..."

> +			For Clk properties, please refer to [1].
> +- interrupts :		Reference to the timer interrupt

Reference to?

See how other binding documents describe this property.

> +Optional parameters:
> +- resets :		Reference to a reset controller asserting the timer

As above.

> +Optional subnodes:

Either use ":" or " :" or "<tab>:", but keep it consistent.

> +- pwm:			See Documentation/devicetree/bindings/pwm/pwm-stm32.txt
> +- iiotimer:		See Documentation/devicetree/bindings/iio/timer/stm32-iio-timer.txt
> +
> +[1] Documentation/devicetree/bindings/clock/clock-bindings.txt

Use the relative paths "../clock/", "../pwm/", "../iio/".

> +Example:
> +	mfd_timer1: mfdtimer1@...10000 {

This is not an "MFD timer".  MFD is a Linuxisum.

> +		compatible = "st,stm32-mfd-timer1";

Better description required.

> +		reg = <0x40010000 0x400>;
> +		clocks = <&rcc 0 160>;
> +		clock-names = "mfd_timer_clk";
> +		interrupts = <27>;
> +
> +		pwm1: pwm1@...10000 {
> +			compatible = "st,stm32-pwm1";
> +		};
> +
> +		iiotimer1: iiotimer1@...10000 {
> +			compatible = "st,stm32-iio-timer1";
> +		};
> +	};

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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