Re: [PATCH v2 2/2] [media] atmel-isc: DT binding for Image Sensor Controller driver

[Wu, Songjun]

Hi Rob,

Thank you for your comments.

On 5/19/2016 07:05, Rob Herring wrote:
> On Wed, May 18, 2016 at 03:46:29PM +0800, Songjun Wu wrote:
> > DT binding documentation for ISC driver.
> >
> > Signed-off-by: Songjun Wu <songjun.wu@xxxxxxxxx>
> > ---
> >
> > 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        | 100 +++++++++++++++++++++
> >  1 file changed, 100 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..9e65395
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/media/atmel-isc.txt
> > @@ -0,0 +1,100 @@
> > +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 ISC;
> > +- 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.
> > +- clk-in-isc
> > +	ISC internal clock node, it includes two clock nodes,
> > +	isc-ispck and isc-mck.
>
> And you need to describe each of these nodes and the properties they
> have. But more on this below...
Should I move the description of clock node below to here?

> > +- atmel,sensor-preferred
> > +	ISC may convert the raw format to the specified format when the sensor
> > +	outputs the raw format, and the sensor may output the specified format
> > +	directly. If sensor is preferred to output the specified format
> > +	directly, the value should be 1 (1-preferred, 0-not).
> > +	The default value is 1.
>
> I don't think this belongs in DT. It sounds more like a configuration
> and userspace decision. It is still not clear what you mean by
> "specified format".
Accept, I will remove this.

> > +
> > +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.
> > +
> > +Required properties for the ISC internal clocks:
> > +- #address-cells
> > +	should be 1 (reg is used to encode clk id).
> > +- #size-cells
> > +	should be 0 (reg is used to encode clk id).
> > +- name
> > +	device tree node describing a ISC internal clock.
> > +	* #clock-cells: from common clock binding; should be set to 0.
> > +	* reg: clock id, there are two values,
> > +	       <0> is ISP clock, <1> is master clock.
> > +	* clocks: shall be the isc internal clock source phandles.
> > +		  e.g. clocks = <&isc_clk>, <&iscck>, <&isc_gclk>;
> > +
> > +Example:
> > +isc: isc@f0008000 {
> > +	compatible = "atmel,sama5d2-isc";
> > +	reg = <0xf0008000 0x4000>;
> > +	interrupts = <46 IRQ_TYPE_LEVEL_HIGH 5>;
> > +	clocks = <&isc_clk>, <&isc_ispck>;
> > +	clock-names = "hclock", "ispck";
> > +	atmel,sensor-preferred = <1>;
> > +
> > +	port {
> > +		#address-cells = <1>;
> > +		#size-cells = <0>;
> > +
> > +		isc_0: endpoint {
> > +			remote-endpoint = <&ov7740_0>;
> > +			hsync-active = <1>;
> > +			vsync-active = <0>;
> > +			pclk-sample = <1>;
> > +		};
> > +	};
> > +
> > +	clk-in-isc {
>
> Is this really separate from the rest of the isc block. It would be
> much more simple to define all the input clocks at the parent and then
> reference these 2 clocks with <&isc 0> and <&isc 1>.
Yes, it's separate from the rest of isc block.
It will register two clocks, one is used in ISC internal processor, the 
other will provide the clock to the sensor outside.
I think it's better that the parent clock is included in node 
'clk-in-isc' node. I will try to optimize this node.

> > +		#address-cells = <1>;
> > +		#size-cells = <0>;
> > +
> > +		isc_ispck: isc-ispck@0 {
>
> These would need a compatible string otherwise.
>
> > +			#clock-cells = <0>;
> > +			reg = <0>;
>
> Are 0 and 1 meaningful in terms of the hardware description?
Yes, It's meaningful.
The register field is different, 0 and 1 can distinguish the different 
clock.

> > +			clocks = <&isc_clk>, <&iscck>;
> > +		};
> > +
> > +		isc_mck: isc-mck@1 {
> > +			#clock-cells = <0>;
> > +			reg = <1>;
> > +			clocks = <&isc_clk>, <&iscck>, <&isc_gclk>;
> > +		};
> > +	};
> > +};