Date:	Mon, 6 Jun 2016 14:44:24 +0800
From:	"Wu, Songjun" <songjun.wu@...el.com>
To:	Boris Brezillon <boris.brezillon@...e-electrons.com>,
	Rob Herring <robh@...nel.org>
CC:	Mark Rutland <mark.rutland@....com>, <devicetree@...r.kernel.org>,
	Pawel Moll <pawel.moll@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	<nicolas.ferre@...el.com>, <linux-kernel@...r.kernel.org>,
	<laurent.pinchart@...asonboard.com>,
	Kumar Gala <galak@...eaurora.org>, <g.liakhovetski@....de>,
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v3 2/2] [media] atmel-isc: DT binding for Image Sensor
 Controller driver



On 6/3/2016 19:10, Boris Brezillon wrote:
> On Thu, 2 Jun 2016 18:16:09 -0500
> Rob Herring <robh@...nel.org> wrote:
>
>> On Tue, May 31, 2016 at 02:58:23PM +0800, Songjun Wu wrote:
>>> DT binding documentation for ISC driver.
>>>
>>> Signed-off-by: Songjun Wu <songjun.wu@...el.com>
>>> ---
>>>
>>> Changes in v3:
>>> - Remove the 'atmel,sensor-preferred'.
>>> - Modify the isc clock node according to the Rob's remarks.
>>>
>>> Changes in v2:
>>> - Remove the unit address of the endpoint.
>>> - Add the unit address to the clock node.
>>> - Avoid using underscores in node names.
>>> - Drop the "0x" in the unit address of the i2c node.
>>> - Modify the description of 'atmel,sensor-preferred'.
>>> - Add the description for the ISC internal clock.
>>>
>>>  .../devicetree/bindings/media/atmel-isc.txt        | 88 ++++++++++++++++++++++
>>>  1 file changed, 88 insertions(+)
>>>  create mode 100644 Documentation/devicetree/bindings/media/atmel-isc.txt
>>>
>>> diff --git a/Documentation/devicetree/bindings/media/atmel-isc.txt b/Documentation/devicetree/bindings/media/atmel-isc.txt
>>> new file mode 100644
>>> index 0000000..2ae1d60
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/media/atmel-isc.txt
>>> @@ -0,0 +1,88 @@
>>> +Atmel Image Sensor Controller (ISC)
>>> +----------------------------------------------
>>> +
>>> +Required properties for ISC:
>>> +- compatible
>>> +	Must be "atmel,sama5d2-isc"
>>> +- reg
>>> +	Physical base address and length of the registers set for the device;
>>> +- interrupts
>>> +	Should contain IRQ line for the ISI;
>>> +- clocks
>>> +	List of clock specifiers, corresponding to entries in
>>> +	the clock-names property;
>>> +	Please refer to clock-bindings.txt.
>>> +- clock-names
>>> +	Required elements: "hclock", "ispck".
>>> +- pinctrl-names, pinctrl-0
>>> +	Please refer to pinctrl-bindings.txt.
>>> +- isc-ispck
>>> +	The clock for the ISC digital pipeline.
>>> +	- compatible
>>> +		Must be "atmel,sama5d2-isc-ispck".
>>> +	- clock-cells
>>> +		From common clock binding; should be set to 0.
>>> +	- clocks
>>> +		The clock source phandles.
>>> +- isc-mck
>>> +	The clock for the image sensor.
>>> +	- compatible
>>> +		Must be "atmel,sama5d2-isc-mck".
>>> +	- clock-cells
>>> +		From common clock binding; should be set to 0.
>>> +	- clocks
>>> +		The clock source phandles.
>>> +
>>> +ISC supports a single port node with parallel bus. It should contain one
>>> +'port' child node with child 'endpoint' node. Please refer to the bindings
>>> +defined in Documentation/devicetree/bindings/media/video-interfaces.txt.
>>> +
>>> +Example:
>>> +isc: isc@...08000 {
>>> +	compatible = "atmel,sama5d2-isc";
>>> +	reg = <0xf0008000 0x4000>;
>>> +	interrupts = <46 IRQ_TYPE_LEVEL_HIGH 5>;
>>> +	clocks = <&isc_clk>, <&isc_ispck>;
>>> +	clock-names = "hclock", "ispck";
>>> +
>>> +	port {
>>> +		#address-cells = <1>;
>>> +		#size-cells = <0>;
>>> +
>>> +		isc_0: endpoint {
>>> +			remote-endpoint = <&ov7740_0>;
>>> +			hsync-active = <1>;
>>> +			vsync-active = <0>;
>>> +			pclk-sample = <1>;
>>> +		};
>>> +	};
>>> +
>>> +	isc_ispck: isc-ispck@0 {
>>
>> Drop the unit-address. You should only have one if you have a reg
>> property.
>>
>>> +		compatible = "atmel,sama5d2-isc-ispck";
>>> +		#clock-cells = <0>;
>>> +		clocks = <&isc_clk>, <&iscck>;
>>> +	};
>>> +
>>> +	isc_mck: isc-mck@1 {
>>
>> ditto.
>>
>> I still think these should be implied by atmel,sama5d2-isc and not in
>> DT. The fact that you don't have any registers for them pretty much
>> indicates that. It is also strange that isc-ispck is used by isc. If
>> that is the only user, there is certainly no need to put it in DT.
>
> I had a look at the block diagram, and it seems you are partially right.
> The only clock that is really exported by the ISC is isc_mck (isc_pck is
> not).
> So I'd suggest dropping these clk sub-nodes, putting the #clock-cells,
> and clock-names properties in the isc node, and then referencing the
> isc node in you i2c device.
>
> isc: isc@...08000 {
> 	compatible = "atmel,sama5d2-isc";
> 	reg = <0xf0008000 0x4000>;
> 	interrupts = <46 IRQ_TYPE_LEVEL_HIGH 5>;
> 	clocks = <&isc_clk>, <&isc_ispck>;
> 	clock-names = "hclock", "ispck";
> 	#clock-cells = <0>;
> 	clock-output-names = "isc-mck";
> };
>
> i2c1: i2c@...28000 {
> 	/* ... */
> 	ov7740: camera@21 {
> 		/* ... */
> 		clocks = <&isc>;
> 		clock-names = "xvclk";
> 	}
> };
>
> If I'm wrong and the ISC IP is really exposing several clks, you just
> have to change #clock-cells to 1, and use clocks = <&isc X>; in the i2c
> device node.
>
> Rob, Songjun, would you agree on this representation?
>
Agree, I think it's a good solution.
Thank you for your comments.
>>
>>
>>> +		compatible = "atmel,sama5d2-isc-mck";
>>> +		#clock-cells = <0>;
>>> +		clocks = <&isc_clk>, <&iscck>, <&isc_gclk>;
>>> +	};
>>> +};
>>> +
>>> +i2c1: i2c@...28000 {
>>> +	ov7740: camera@21 {
>>> +	compatible = "ovti,ov7740";
>>> +	reg = <0x21>;
>>> +
>>> +	clocks = <&isc_mck>;
>>> +	clock-names = "xvclk";
>>> +	assigned-clocks = <&isc_mck>;
>>> +	assigned-clock-rates = <24000000>;
>>> +
>>> +	port {
>>> +		ov7740_0: endpoint {
>>> +			remote-endpoint = <&isc_0>;
>>> +		};
>>> +	};
>>> +};
>>> --
>>> 2.7.4
>>>
>>
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>> linux-arm-kernel@...ts.infradead.org
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>
>
>

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