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Date:   Sun, 19 Apr 2020 18:43:05 +0300
From:   Laurent Pinchart <laurent.pinchart@ideasonboard.com>
To:     Vishal Sagar <vishal.sagar@xilinx.com>
Cc:     Hyun Kwon <hyunk@xilinx.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>,
        Luca Ceresoli <luca@lucaceresoli.net>,
        Jacopo Mondi <jacopo@jmondi.org>,
        Hyun Kwon <hyun.kwon@xilinx.com>, Rob Herring <robh@kernel.org>
Subject: Re: [PATCH v11 1/2] media: dt-bindings: media: xilinx: Add Xilinx
 MIPI CSI-2 Rx Subsystem
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References: <20200409194424.45555-1-vishal.sagar@xilinx.com>
 <20200409194424.45555-2-vishal.sagar@xilinx.com>
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Hi Vishal,

Thank you for the patch.

On Fri, Apr 10, 2020 at 01:14:23AM +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.

The AXI IIC was removed from the subsystem in v4.1, you could drop it
from the commit message too.

> 
> Signed-off-by: Vishal Sagar <vishal.sagar@xilinx.com>
> Reviewed-by: Hyun Kwon <hyun.kwon@xilinx.com>
> Reviewed-by: Rob Herring <robh@kernel.org>
> Reviewed-by: Luca Ceresoli <luca@lucaceresoli.net>
> ---
> v11
> - Modify compatible string from 4.0 to 5.0
> 
> v10
> - No changes
> 
> v9
> - Fix xlnx,vfb description.
> - s/Optional/Required endpoint property.
> - Move data-lanes description from Ports to endpoint property section.
> 
> v8
> - Added reset-gpios optional property to assert video_aresetn
> 
> v7
> - Removed the control name from dt bindings
> - Updated the example dt node name to csi2rx
> 
> 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   | 116 ++++++++++++++++++
>  1 file changed, 116 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 000000000000..9269a5c880aa
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/media/xilinx/xlnx,csi2rxss.txt

YAML is the recommended form for new DT bindings. This wasn't a
requirement when the first version of this series was submitted, and I
understand it can be frustrating to chase a moving target, so I can help
with the YAML conversion once we sort out the questions below.

> @@ -0,0 +1,116 @@
> +Xilinx MIPI CSI2 Receiver Subsystem Device Tree Bindings

Nitpicking, it's CSI-2, not CSI2.

> +--------------------------------------------------------
> +
> +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

And D-PHY, not DPHY :-)

> +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.

If I understand correctly, this DT binding covers the CSI-2 RX
Controller and the optional Video Format Bridge, but leaves the D-PHY
out, right ? I think this should be clarified, as the "CSI-2 receiver
subsystem" includes the D-PHY.

> +
> +Required properties:
> +--------------------
> +- compatible: Must contain "xlnx,mipi-csi2-rx-subsystem-5.0".

Is PG232 v5.0 available ? The most recent version I've found was PG232
v4.1.

> +- 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.

The subsystem documentation also mentions a dphy_clk_200M. Is that
routed to the D-PHY only, or is it also needed for the CSI-2 RX ?

> +- 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

Isn't this property required only when the VFB is present ?

> +
> +
> +Optional properties:
> +--------------------
> +- xlnx,vfb: Present when Video Format Bridge is enabled in IP configuration
> +- xlnx,en-csi-v2-0: Present if CSI v2 is enabled in IP configuration.

Unless I'm mistaken, this feature is available starting at v4 of the IP
core.

> +- 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
> +  re-configured at runtime in the Protocol Configuration Register.
> +  Otherwise all lanes, as set in IP configuration, are always active.
> +- reset-gpios: Optional specifier for a GPIO that asserts video_aresetn.

Should lite_aresetn also be supported ? We can add a lite-reset-gpios
property later, but maybe we should name this video-reset-gpios ? As the
video_aresetn signal is the main reset I don't mind keeping the name
reset-gpios either. It's up to you.

> +
> +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.
> +
> +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.

Don't you need a second source port for embedded non-image data ? If my
understanding is correct that port can be enabled or disabled through
the CSI_EMB_NON_IMG parameter, so it should be optional in DT too. We
can possibly leave it out for now, it can be added later in a
backward-compatible way.

> +
> +Required endpoint property:
> +---------------------------
> +- data-lanes: specifies MIPI CSI-2 data lanes as covered in video-interfaces.txt.
> +  This is required only in the sink port 0 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:
> +
> +	xcsi2rxss_1: csi2rx@a0020000 {
> +		compatible = "xlnx,mipi-csi2-rx-subsystem-5.0";
> +		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>;
> +		reset-gpios = <&gpio 86 GPIO_ACTIVE_LOW>;
> +
> +		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>;
> +				};
> +			};
> +		};
> +	};

-- 
Regards,

Laurent Pinchart