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Date:   Tue, 12 Jun 2018 14:03:38 -0600
From:   Rob Herring <robh@kernel.org>
To:     Vishal Sagar <vishal.sagar@xilinx.com>
Cc:     hyun.kwon@xilinx.com, laurent.pinchart@ideasonboard.com,
        michal.simek@xilinx.com, linux-media@vger.kernel.org,
        devicetree@vger.kernel.org, mark.rutland@arm.com,
        mchehab@kernel.org, linux-kernel@vger.kernel.org,
        hans.verkuil@cisco.com, sakari.ailus@linux.intel.com,
        dineshk@xilinx.com, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 1/2] media: dt-bindings: media: xilinx: Add Xilinx MIPI
 CSI-2 Rx Subsystem
Message-ID: <20180612200338.GA31620@rob-hp-laptop>
References: <1527620084-94864-1-git-send-email-vishal.sagar@xilinx.com>
 <1527620084-94864-2-git-send-email-vishal.sagar@xilinx.com>
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On Wed, May 30, 2018 at 12:24:43AM +0530, Vishal Sagar wrote:
> Add bindings documentation for Xilinx MIPI CSI-2 Rx Subsystem.
> 
> The Xilinx MIPI CSI-2 Rx Subsystem consists of a DPHY, CSI-2 Rx, an
> optional I2C controller and an optional Video Format Bridge (VFB). The
> active lanes can be configured at run time if enabled in the IP. The
> DPHY register interface may also be enabled.
>
> Signed-off-by: Vishal Sagar <vishal.sagar@xilinx.com>
> ---
>  .../bindings/media/xilinx/xlnx,csi2rxss.txt        | 117 +++++++++++++++++++++
>  1 file changed, 117 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..31ed721
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/media/xilinx/xlnx,csi2rxss.txt
> @@ -0,0 +1,117 @@
> +
> +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. This data is taken in by the Video Format Bridge (VFB),
> +if selected, and converted into AXI4 Stream video data at selected
> +pixels per clock as per AXI4-Stream Video IP and System Design UG934.
> +
> +For more details, please refer to PG232 MIPI CSI-2 Receiver Subsystem.
> +https://www.xilinx.com/support/documentation/ip_documentation/mipi_csi2_rx_subsystem/v3_0/pg232-mipi-csi2-rx.pdf
> +
> +Required properties:
> +
> +- compatible: Must contain "xlnx,mipi-csi2-rx-subsystem-2.0" or
> +  "xlnx,mipi-csi2-rx-subsystem-3.0"
> +
> +- reg: Physical base address and length of the registers set for the device.
> +
> +- interrupt-parent: specifies the phandle to the parent interrupt controller
> +
> +- interrupts: Property with a value describing the interrupt number.
> +
> +- xlnx,max-lanes: Maximum active lanes in the design.

There's already a property defined in video-interfaces.txt to limit 
lanes.

> +
> +- xlnx,vc: Virtual Channel, specifies virtual channel number to be filtered.
> +  If this is 4 then all virtual channels are allowed.
> +
> +- 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 RAW6, RAW7, RAW8, RAW10,
> +  RAW12, RAW14, RGB444, RGB555, RGB565, RGB666, RGB888 and YUV4228bit.

This should be standard property. 

> +
> +- xlnx,axis-tdata-width: AXI Stream width, This denotes the AXI Stream width.
> +  It depends on Data type chosen, Video Format Bridge enabled/disabled and
> +  pixels per clock. If VFB is disabled then its value is either 0x20 (32 bit)
> +  or 0x40(64 bit) width.
> +
> +- xlnx,video-format, xlnx,video-width: Video format and width, as defined in
> +  video.txt.

This doc needs to define what are valid values.

Why do you need this on both ports? Can there be a conversion in this 
block? At least for the MIPI CSI interface part, this should be a common 
property. Not sure offhand if we have defined one. We have for parallel 
interfaces.

And 'width' doesn't seem like the right term for what this is defined to 
be.

> +
> +- port: Video port, using the DT bindings defined in ../video-interfaces.txt.

port is not a property. It goes in its own section. And port properties 
should be under it.

> +  The CSI 2 Rx Subsystem has a two ports, one input port for connecting to
> +  camera sensor and other is output port.

Need be specific port #0 is ?? and port #1 is ??.

> +
> +- data-lanes: The number of data lanes through which CSI2 Rx Subsystem is
> +  connected to the camera sensor as per video-interfaces.txt

Why do you need both this and max-lanes?

> +
> +Optional properties:
> +
> +- xlnx,en-active-lanes: Enable Active lanes configuration in Protocol
> +  Configuration Register.
> +
> +- xlnx,dphy-present: This is equivalent to whether DPHY register interface is
> +  enabled or not.
> +
> +- xlnx,iic-present: This shows whether subsystem's IIC is present or not. This
> +  affects the base address of the DPHY.

Perhaps you should break up reg into ranges for each submodule (or make 
the DPHY a separate node and use the phy binding.

> +
> +- xlnx,vfb: Video Format Bridge, Denotes if Video Format Bridge is selected
> +  so that output is as per AXI stream documented in UG934.
> +
> +- xlnx,ppc: Pixels per clock, Number of pixels to be transferred per pixel
> +  clock. This is valid only if xlnx,vfb property is present.
> +
> +Example:
> +
> +       csiss_1: csiss@a0020000 {
> +               compatible = "xlnx,mipi-csi2-rx-subsystem-3.0";
> +               reg = <0x0 0xa0020000 0x0 0x20000>;
> +               interrupt-parent = <&gic>;
> +               interrupts = <0 95 4>;
> +
> +               xlnx,max-lanes = <0x4>;
> +               xlnx,en-active-lanes;
> +               xlnx,dphy-present;
> +               xlnx,iic-present;
> +               xlnx,vc = <0x4>;
> +               xlnx,csi-pxl-format = "RAW8";
> +               xlnx,vfb;
> +               xlnx,ppc = <0x4>;
> +               xlnx,axis-tdata-width = <0x20>;
> +
> +               ports {
> +                       #address-cells = <1>;
> +                       #size-cells = <0>;
> +
> +                       port@0 {
> +                               reg = <0>;
> +
> +                               xlnx,video-format = <XVIP_VF_YUV_422>;
> +                               xlnx,video-width = <8>;
> +                               csiss_out: endpoint {
> +                                       remote-endpoint = <&vcap_csiss_in>;
> +                               };
> +                       };
> +                       port@1 {
> +                               reg = <1>;
> +
> +                               xlnx,video-format = <XVIP_VF_YUV_422>;
> +                               xlnx,video-width = <8>;
> +
> +                               csiss_in: endpoint {
> +                                       data-lanes = <1 2 3 4>;
> +                                       /* MIPI CSI2 Camera handle */
> +                                       remote-endpoint = <&vs2016_out>;
> +                               };
> +
> +                       };
> +
> +               };
> +       };
> --
> 2.7.4
> 
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