linux-kernel - Re: [PATCH 2/2] dt-bindings: iio: imu: adis16480: Document external clock

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Date:   Fri, 8 Mar 2019 15:07:28 +0000
From:   Jonathan Cameron <jonathan.cameron@...wei.com>
To:     Stefan Popa <stefan.popa@...log.com>
CC:     <jic23@...nel.org>, <robh+dt@...nel.org>, <mark.rutland@....com>,
        <knaack.h@....de>, <lars@...afoo.de>, <pmeerw@...erw.net>,
        <Michael.Hennerich@...log.com>, <gregkh@...uxfoundation.org>,
        <linux-iio@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] dt-bindings: iio: imu: adis16480: Document external
 clock

On Thu, 7 Mar 2019 17:29:19 +0200
Stefan Popa <stefan.popa@...log.com> wrote:

> Add documentation for optional use of external clock. All devices
> supported by this driver can work with an external clock in sync mode.
> Another mode, called Pulse Per Second (PPS) is supported only by adis1649x
> devices. The mode is selected by using the "clock-names" property.
> 
> The pin which is used as external clock input is selected by using a
> custom optional property called "adi,ext-clk-pin". If this field is left
> empty, DIO2 is assigned as default external clock input pin.
> 
> Signed-off-by: Stefan Popa <stefan.popa@...log.com>
Trivial comments inline...

Thanks,

Jonathan

> ---
>  .../devicetree/bindings/iio/imu/adi,adis16480.txt  | 34 ++++++++++++++++++++++
>  1 file changed, 34 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/iio/imu/adi,adis16480.txt b/Documentation/devicetree/bindings/iio/imu/adi,adis16480.txt
> index 39ab016..9e2fcd4 100644
> --- a/Documentation/devicetree/bindings/iio/imu/adi,adis16480.txt
> +++ b/Documentation/devicetree/bindings/iio/imu/adi,adis16480.txt
> @@ -34,6 +34,37 @@ Optional properties:
>  	signal.
>  - reset-gpios: must be the device tree identifier of the RESET pin. As the line
>  	is active low, it should be marked GPIO_ACTIVE_LOW.
> +- clocks: phandle to the external clock. Should be set according to
> +	"clock-names".
> +	If this field is left empty, the internal clock is used.
> +- clock-names: The name of the external clock to be used. Valid values are:
> +	* sync: In sync mode, the internal clock is disabled and the frequency
> +		of the external clock signal establishes therate of data
the rate
> +		collection and processing. See Fig 14 and 15 in the datasheet.
> +		The clock-frequency must be:
> +		* 3000 to 4500 Hz for adis1649x devices.
> +		* 700 to 2400 Hz for adis1648x devices.
> +	* pps: In Pulse Per Second (PPS) Mode, the rate of data collection and
> +	       production is equal to the product of the external clock
> +	       frequency and the scale factor in the SYNC_SCALE register, see
> +	       Table 154 in the datasheet.
> +	       The clock-frequency must be:
> +	       * 1 to 128 Hz for adis1649x devices.
> +	       * This mode is not supported by adis1648x devices.
> +	If this field is left empty, the internal clock is used.

Should we say that both clocks and clock-names should be empty if that is
the intent?

> +- adi,ext-clk-pin: The DIOx line to be used as an external clock input.
> +	Valid values are:
> +	* DIO1
> +	* DIO2
> +	* DIO3
> +	* DIO4
> +	Each DIOx pin supports only one function at a time (data ready line
> +	selection or external clock input). When a single pin has two
> +	two assignments, the enable bit for the lower priority function
> +	automatically resets to zero (disabling the lower priority function).
> +	Data ready has highest priority.
> +	If this field is left empty, DIO2 is assigned as default external clock
> +	input pin.
>  
>  Example:
>  
> @@ -46,4 +77,7 @@ Example:
>  		interrupts = <25 IRQF_TRIGGER_FALLING>;
>  		interrupt-parent = <&gpio>;
>  		interrupt-names = "DIO2";
> +		clocks = <&adis16495_sync>;
> +		clock-names = "sync";
> +		adi,ext-clk-pin = "DIO1";
>  	};