Subject: [PATCH v4 02/10] Documentation: dt: Add DT binding documentation for S5C73M3 camera

From: [email-masked] (Sylwester Nawrocki)
Date: Fri, 21 Feb 2014 18:52:50 +0100

On 21/02/14 16:42, Mark Rutland wrote:
[...]
>> +++ b/Documentation/devicetree/bindings/media/samsung-s5c73m3.txt
>> @@ -0,0 +1,97 @@
>> +Samsung S5C73M3 8Mp camera ISP
>> +------------------------------
>> +
>> +The S5C73M3 camera ISP supports MIPI CSI-2 and parallel (ITU-R BT.656) video
>> +data busses. The I2C bus is the main control bus and additionally the SPI bus
>> +is used, mostly for transferring the firmware to and from the device. Two
>> +slave device nodes corresponding to these control bus interfaces are required
>> +and should be placed under respective bus controller nodes.
> 
> So this has both an I2C interface and an SPI interface that are used at
> the same time?

Yes, both are needed. AFAIU SPI is added so the firmware upload is faster.

>> +I2C slave device node
>> +---------------------
>> +
>> +Required properties:
>> +
>> +- compatible	    : "samsung,s5c73m3";
>> +- reg		    : I2C slave address of the sensor;
>> +- vdd-int-supply    : digital power supply (1.2V);
>> +- vdda-supply	    : analog power supply (1.2V);
>> +- vdd-reg-supply    : regulator input power supply (2.8V);
>> +- vddio-host-supply : host I/O power supply (1.8V to 2.8V);
>> +- vddio-cis-supply  : CIS I/O power supply (1.2V to 1.8V);
>> +- vdd-af-supply     : lens power supply (2.8V);
>> +- xshutdown-gpios   : specifier of GPIO connected to the XSHUTDOWN pin;
>> +- standby-gpios     : specifier of GPIO connected to the STANDBY pin;
>> +- clocks	    : should contain list of phandle and clock specifier pairs
>> +		      according to common clock bindings for the clocks described
>> +		      in the clock-names property;
>> +- clock-names	    : should contain "cis_extclk" entry for the CIS_EXTCLK clock;
>> +
>> +Optional properties:
>> +
>> +- clock-frequency   : the frequency at which the "cis_extclk" clock should be
>> +		      configured to operate, in Hz; if this property is not
>> +		      specified default 24 MHz value will be used.
>> +
>> +The common video interfaces bindings (see video-interfaces.txt) should be used
>> +to specify link from the S5C73M3 to an external image data receiver. The S5C73M3
>> +device node should contain one 'port' child node with an 'endpoint' subnode for
>> +this purpose. The data link from a raw image sensor to the S5C73M3 can be
>> +similarly specified, but it is optional since the S5C73M3 ISP and a raw image
>> +sensor are usually inseparable and form a hybrid module.
>> +
>> +Following properties are valid for the endpoint node(s):
>> +
>> +endpoint subnode
>> +----------------
>> +
>> +- data-lanes : (optional) specifies MIPI CSI-2 data lanes as covered in
>> +  video-interfaces.txt. This sensor doesn't support data lane remapping
>> +  and physical lane indexes in subsequent elements of the array should
>> +  be only consecutive ascending values.
>> +
>> +SPI device node
>> +---------------
>> +
>> +Required properties:
>> +
>> +- compatible	    : "samsung,s5c73m3";
> 
> It might make sense to explicitly link these two nodes somehow, in case
> multiple instances appear somewhere. However, that can come later in the
> case of a multi-instance device, and isn't necessary now.

I guess a phandle at the I2C slave device node, pointing to the SPI node
and/or the other way around would do. I don't expect these devices to be 
used in multiple instances though and would prefer to address that when
necessary.

We could try and create a root node for this device with an interesting 
structure, if we wanted to go much into details. But it could get a bit 
complicated given the scheme the I2C/SPI bus binding are structured now.
Presumably that's something that could be handled later with a different 
compatible string if required.

>> +For more details see description of the SPI busses bindings
>> +(../spi/spi-bus.txt) and bindings of a specific bus controller.
>> +
>> +Example:
>> +
>> +i2c at 138A000000 {
>> +	...
>> +	s5c73m3 at 3c {
>> +		compatible = "samsung,s5c73m3";
>> +		reg = <0x3c>;
>> +		vdd-int-supply = <&buck9_reg>;
>> +		vdda-supply = <&ldo17_reg>;
>> +		vdd-reg-supply = <&cam_io_reg>;
>> +		vddio-host-supply = <&ldo18_reg>;
>> +		vddio-cis-supply = <&ldo9_reg>;
>> +		vdd-af-supply = <&cam_af_reg>;
>> +		clock-frequency = <24000000>;
>> +		clocks = <&clk 0>;
>> +		clock-names = "cis_extclk";
>> +		reset-gpios = <&gpf1 3 1>;
>> +		standby-gpios = <&gpm0 1 1>;
>> +		port {
>> +			s5c73m3_ep: endpoint {
>> +				remote-endpoint = <&csis0_ep>;
>> +				data-lanes = <1 2 3 4>;
>> +			};
>> +		};
>> +	};
>> +};
>> +
>> +spi at 1392000 {
>> +	...
>> +	s5c73m3_spi: s5c73m3 {
> 
> Nit: this should have a 0 unit-address to match the reg.

OK, I'll correct that.

>> +		compatible = "samsung,s5c73m3";
>> +		reg = <0>;
>> +		...
>> +	};
>> +};
> 
> Otherwise I don't see anything problematic about the binding.
> 
> Acked-by: Mark Rutland <[email-masked]>

Thanks for the review.

--
Regards,
Sylwester