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Date:   Tue, 12 Mar 2019 12:21:18 +0200
From:   Sakari Ailus <sakari.ailus@linux.intel.com>
To:     Vishal Sagar <vishal.sagar@xilinx.com>
Cc:     Hyun Kwon <hyunk@xilinx.com>, laurent.pinchart@ideasonboard.com,
        mchehab@kernel.org, robh+dt@kernel.org, mark.rutland@arm.com,
        Michal Simek <michals@xilinx.com>, linux-media@vger.kernel.org,
        devicetree@vger.kernel.org, hans.verkuil@cisco.com,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        Dinesh Kumar <dineshk@xilinx.com>,
        Sandip Kothari <sandipk@xilinx.com>
Subject: Re: [PATCH v6 1/2] media: dt-bindings: media: xilinx: Add Xilinx
 MIPI CSI-2 Rx Subsystem
Message-ID: <20190312102118.6ianedkzscr7gdba@kekkonen.localdomain>
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Hi Vishal,

Thanks for the update. This looks pretty good, please see a few comments
below.

On Tue, Mar 12, 2019 at 10:05:29AM +0530, Vishal Sagar wrote:
> Add bindings documentation for Xilinx MIPI CSI-2 Rx Subsystem.
> 
> The Xilinx MIPI CSI-2 Rx Subsystem consists of a CSI-2 Rx controller, a
> DPHY in Rx mode, an optional I2C controller and a Video Format Bridge.
> 
> Signed-off-by: Vishal Sagar <vishal.sagar@xilinx.com>
> Reviewed-by: Hyun Kwon <hyun.kwon@xilinx.com>
> Reviewed-by: Rob Herring <robh@kernel.org>
> ---
> v6
> - Added "control" after V4L2_CID_XILINX_MIPICSISS_ACT_LANES as suggested by Luca
> - Added reviewed by Rob Herring
> 
> v5
> - Incorporated comments by Luca Cersoli
> - Removed DPHY clock from description and example
> - Removed bayer pattern from device tree MIPI CSI IP
>   doesn't deal with bayer pattern.
> 
> v4
> - Added reviewed by Hyun Kwon
> 
> v3
> - removed interrupt parent as suggested by Rob
> - removed dphy clock
> - moved vfb to optional properties
> - Added required and optional port properties section
> - Added endpoint property section
> 
> v2
> - updated the compatible string to latest version supported
> - removed DPHY related parameters
> - added CSI v2.0 related property (including VCX for supporting upto 16
>   virtual channels).
> - modified csi-pxl-format from string to unsigned int type where the value
>   is as per the CSI specification
> - Defined port 0 and port 1 as sink and source ports.
> - Removed max-lanes property as suggested by Rob and Sakari
> 
>  .../bindings/media/xilinx/xlnx,csi2rxss.txt        | 118 +++++++++++++++++++++
>  1 file changed, 118 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/media/xilinx/xlnx,csi2rxss.txt
> 
> diff --git a/Documentation/devicetree/bindings/media/xilinx/xlnx,csi2rxss.txt b/Documentation/devicetree/bindings/media/xilinx/xlnx,csi2rxss.txt
> new file mode 100644
> index 0000000..5b8170f
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/media/xilinx/xlnx,csi2rxss.txt
> @@ -0,0 +1,118 @@
> +Xilinx MIPI CSI2 Receiver Subsystem Device Tree Bindings
> +--------------------------------------------------------
> +
> +The Xilinx MIPI CSI2 Receiver Subsystem is used to capture MIPI CSI2 traffic
> +from compliant camera sensors and send the output as AXI4 Stream video data
> +for image processing.
> +
> +The subsystem consists of a MIPI DPHY in slave mode which captures the
> +data packets. This is passed along the MIPI CSI2 Rx IP which extracts the
> +packet data. The optional Video Format Bridge (VFB) converts this data to
> +AXI4 Stream video data.
> +
> +For more details, please refer to PG232 Xilinx MIPI CSI-2 Receiver Subsystem.
> +
> +Required properties:
> +--------------------
> +- compatible: Must contain "xlnx,mipi-csi2-rx-subsystem-4.0".
> +- reg: Physical base address and length of the registers set for the device.
> +- interrupts: Property with a value describing the interrupt number.
> +- clocks: List of phandles to AXI Lite and Video clocks.
> +- clock-names: Must contain "lite_aclk" and "video_aclk" in the same order
> +  as clocks listed in clocks property.
> +- xlnx,csi-pxl-format: This denotes the CSI Data type selected in hw design.
> +  Packets other than this data type (except for RAW8 and User defined data
> +  types) will be filtered out. Possible values are as below -
> +  0x1E - YUV4228B
> +  0x1F - YUV42210B
> +  0x20 - RGB444
> +  0x21 - RGB555
> +  0x22 - RGB565
> +  0x23 - RGB666
> +  0x24 - RGB888
> +  0x28 - RAW6
> +  0x29 - RAW7
> +  0x2A - RAW8
> +  0x2B - RAW10
> +  0x2C - RAW12
> +  0x2D - RAW14
> +  0x2E - RAW16
> +  0x2F - RAW20
> +
> +
> +Optional properties:
> +--------------------
> +- xlnx,vfb: This is present when Video Format Bridge is enabled.
> +  Without this property the driver won't be loaded as IP won't be able to generate
> +  media bus format compliant stream output.

What's the use case for this? I read in an earlier thread that this is
used to prevent the driver from loading.

> +- xlnx,en-csi-v2-0: Present if CSI v2 is enabled in IP configuration.
> +- xlnx,en-vcx: When present, there are maximum 16 virtual channels, else
> +  only 4. This is present only if xlnx,en-csi-v2-0 is present.
> +- xlnx,en-active-lanes: present if the number of active lanes can be
> +  reconfigured at runtime in the Protocol Configuration Register.
> +  If present, the V4L2_CID_XILINX_MIPICSISS_ACT_LANES control is added.
> +  Otherwise all lanes, as set in IP configuration, are always active.

The bindings document hardware, therefore a V4L2 control name doesn't
belong here.

If you want to set the number of lanes at runtime, the frame descriptors
are probably the best way to do that. The patchset will be merged in the
near future. Jacopo sent the last iteration of it recently. I'd leave that
feature out for now though: few transmitter drivers support the feature
(using an old API).

> +
> +Ports
> +-----
> +The device node shall contain two 'port' child nodes as defined in
> +Documentation/devicetree/bindings/media/video-interfaces.txt.
> +
> +The port@0 is a sink port and shall connect to CSI2 source like camera.
> +It must have the data-lanes property.
> +
> +The port@1 is a source port and can be connected to any video processing IP
> +which can work with AXI4 Stream data.
> +
> +Required port properties:
> +--------------------
> +- reg: 0 - for sink port.
> +       1 - for source port.
> +
> +Optional endpoint property:
> +---------------------------
> +- data-lanes: specifies MIPI CSI-2 data lanes as covered in video-interfaces.txt.
> +  This should be in the sink port endpoint which connects to MIPI CSI2 source
> +  like sensor. The possible values are:
> +  1       - For 1 lane enabled in IP.
> +  1 2     - For 2 lanes enabled in IP.
> +  1 2 3   - For 3 lanes enabled in IP.
> +  1 2 3 4 - For 4 lanes enabled in IP.
> +
> +Example:
> +
> +	csiss_1: csiss@a0020000 {

The node name should be generic, a Cadence device uses csi2rx which seems
like a good fit here, too.

> +		compatible = "xlnx,mipi-csi2-rx-subsystem-4.0";
> +		reg = <0x0 0xa0020000 0x0 0x10000>;
> +		interrupt-parent = <&gic>;
> +		interrupts = <0 95 4>;
> +		xlnx,csi-pxl-format = <0x2a>;
> +		xlnx,vfb;
> +		xlnx,en-active-lanes;
> +		xlnx,en-csi-v2-0;
> +		xlnx,en-vcx;
> +		clock-names = "lite_aclk", "video_aclk";
> +		clocks = <&misc_clk_0>, <&misc_clk_1>;
> +
> +		ports {
> +			#address-cells = <1>;
> +			#size-cells = <0>;
> +
> +			port@0 {
> +				/* Sink port */
> +				reg = <0>;
> +				csiss_in: endpoint {
> +					data-lanes = <1 2 3 4>;
> +					/* MIPI CSI2 Camera handle */
> +					remote-endpoint = <&camera_out>;
> +				};
> +			};
> +			port@1 {
> +				/* Source port */
> +				reg = <1>;
> +				csiss_out: endpoint {
> +					remote-endpoint = <&vproc_in>;
> +				};
> +			};
> +		};
> +	};

-- 
Kind regards,

Sakari Ailus
sakari.ailus@linux.intel.com