Date:   Wed, 27 May 2020 11:40:45 +0000
From:   Vishal Sagar <vsagar@...inx.com>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>
CC:     Hyun Kwon <hyunk@...inx.com>,
        "mchehab@...nel.org" <mchehab@...nel.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "hans.verkuil@...co.com" <hans.verkuil@...co.com>,
        Luca Ceresoli <luca@...aceresoli.net>,
        Jacopo Mondi <jacopo@...ndi.org>,
        Michal Simek <michals@...inx.com>,
        "linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Dinesh Kumar <dineshk@...inx.com>,
        Sandip Kothari <sandipk@...inx.com>,
        Rob Herring <robh@...nel.org>
Subject: RE: [PATCH v12 1/2] media: dt-bindings: media: xilinx: Add Xilinx
 MIPI CSI-2 Rx Subsystem

Hi Laurent,

> -----Original Message-----
> From: Laurent Pinchart <laurent.pinchart@...asonboard.com>
> Sent: Sunday, May 24, 2020 7:16 AM
> To: Vishal Sagar <vsagar@...inx.com>
> Cc: Hyun Kwon <hyunk@...inx.com>; mchehab@...nel.org;
> robh+dt@...nel.org; mark.rutland@....com; hans.verkuil@...co.com; Luca
> Ceresoli <luca@...aceresoli.net>; Jacopo Mondi <jacopo@...ndi.org>;
> Michal Simek <michals@...inx.com>; linux-media@...r.kernel.org;
> devicetree@...r.kernel.org; linux-arm-kernel@...ts.infradead.org; linux-
> kernel@...r.kernel.org; Dinesh Kumar <dineshk@...inx.com>; Sandip Kothari
> <sandipk@...inx.com>; Rob Herring <robh@...nel.org>
> Subject: Re: [PATCH v12 1/2] media: dt-bindings: media: xilinx: Add Xilinx MIPI
> CSI-2 Rx Subsystem
> 
> Hi Vishal,
> 
> On Fri, May 08, 2020 at 01:52:36PM +0000, Vishal Sagar wrote:
> > On Tuesday, May 5, 2020 7:53 PM, Laurent Pinchart wrote:
> > > On Thu, Apr 23, 2020 at 09:00:37PM +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 D-PHY in Rx mode and a Video Format Bridge.
> > > >
> > > > Signed-off-by: Vishal Sagar <vishal.sagar@...inx.com>
> > > > Reviewed-by: Hyun Kwon <hyun.kwon@...inx.com>
> > > > Reviewed-by: Rob Herring <robh@...nel.org>
> > > > Reviewed-by: Luca Ceresoli <luca@...aceresoli.net>
> > > > ---
> > > > v12
> > > > - Moved to yaml format
> > > > - Update CSI-2 and D-PHY
> > > > - Mention that bindings for D-PHY not here
> > > > - reset -> video-reset
> > > >
> > > > 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.yaml  | 215
> > > > ++++++++++++++++++
> > > >  1 file changed, 215 insertions(+)  create mode 100644
> > > > Documentation/devicetree/bindings/media/xilinx/xlnx,csi2rxss.yaml
> > > >
> > > > diff --git
> > > > a/Documentation/devicetree/bindings/media/xilinx/xlnx,csi2rxss.yam
> > > > l
> > > > b/Documentation/devicetree/bindings/media/xilinx/xlnx,csi2rxss.yam
> > > > l
> > > > new file mode 100644
> > > > index 000000000000..365084e27f7e
> > > > --- /dev/null
> > > > +++ b/Documentation/devicetree/bindings/media/xilinx/xlnx,csi2rxss
> > > > +++ .yam
> > > > +++ l
> > > > @@ -0,0 +1,215 @@
> > > > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) %YAML
> > > > +1.2
> > > > +---
> > > > +$id:
> > > > +http://devicetree.org/schemas/media/xilinx/xlnx,csi2rxss.yaml#
> > > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > > +
> > > > +title: Xilinx MIPI CSI-2 Receiver Subsystem
> > > > +
> > > > +maintainers:
> > > > +  - Vishal Sagar <vishal.sagar@...inx.com>
> > > > +
> > > > +description: |
> > > > +  The Xilinx MIPI CSI-2 Receiver Subsystem is used to capture
> > > > +MIPI CSI-2
> > > > +  traffic from compliant camera sensors and send the output as
> > > > +AXI4 Stream
> > > > +  video data for image processing.
> > > > +  The subsystem consists of a MIPI D-PHY in slave mode which
> > > > +captures the
> > > > +  data packets. This is passed along the MIPI CSI-2 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.
> > > > +  Please note that this bindings includes only the MIPI CSI-2 Rx
> > > > +controller
> > > > +  and Video Format Bridge and not D-PHY.
> > >
> > > How should the D-PHY be handled, when DPY_EN_REG_IF is set to true ?
> >
> > It was suggested in v3 to have a separate D-PHY phy driver which would be
> initialized / configured from MIPI CSI-2 Rx driver.
> > Currently with the D-PHY register interface enabled, we don't have to
> > really configure anything but the following parameters
> > 1 - init
> > 2 - hs_settle
> > 3 - hs_timeout (High Speed mode timeout)
> > 4 - esc_timeout  (Escape mode timeout)
> > 5 - idelay tap
> >
> > The D-PHY Rx can be enabled/disabled and has a soft reset bit.
> > The HS and Escape mode timeout registers can be enabled with a default
> value via the Vivado IP GUI.
> >
> > The above parameters would have to be passed to D-PHY driver as custom
> > control via MIPI CSI-2 Rx driver as these depend on the sensor connected.
> > Probably these can be a new common control in V4L2 framework for CSI Rx
> controllers.
> 
> It seems that in that case, regardless of whether we go for a separate PHY
> driver or not, we will be able to extend the DT bindings, either with a phys
> property, or with an additional reg entry. That should be backward-
> compatible, so I'm not concerned.
> 
> > > > +
> > > > +properties:
> > > > +  compatible:
> > > > +    items:
> > > > +      - enum:
> > > > +        - xlnx,mipi-csi2-rx-subsystem-5.0
> > > > +
> > > > +  reg:
> > > > +    maxItems: 1
> > > > +
> > > > +  interrupts:
> > > > +    maxItems: 1
> > > > +
> > > > +  clocks:
> > > > +    description: List of clock specifiers
> > > > +    items:
> > > > +      - description: AXI Lite clock
> > > > +      - description: Video clock
> > > > +
> > > > +  clock-names:
> > > > +    items:
> > > > +      - const: lite_aclk
> > > > +      - const: video_aclk
> > > > +
> > > > +  xlnx,csi-pxl-format:
> > > > +    description: |
> > > > +      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
> > > > +    allOf:
> > > > +      - $ref: /schemas/types.yaml#/definitions/uint32
> > > > +      - enum: [0x1e, 0x1f, 0x20, 0x21, 0x22, 0x23, 0x24, 0x28,
> > > > + 0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f]
> > >
> > > This could also be written
> > >
> > >     allOf:
> > >       - $ref: /schemas/types.yaml#/definitions/uint32
> > >       - anyOf:
> > >         - minimum: 0x1e
> > >           maximum: 0x24
> > >         - minimum: 0x28
> > >           maximum: 0x2f
> > >
> > > if you want to make it a bit more compact (in the number of values,
> > > not the number of lines obviously), up to you.
> >
> > Thanks for sharing this method. I will update this in next version.
> >
> > > I will also quote the question (and your answer) from the previous
> > > version:
> > >
> > > > > Isn't this property required only when the VFB is present ?
> > > >
> > > > This will be present irrespective of VFB being enabled.
> > > > With VFB, the data on the bus will be as per Xilinx UG934 which is similar
> to media bus formats.
> > > >
> > > > Without VFB, it will just be plain data as it comes in data packets.
> > > > Refer to the Xilinx PG 232 "Pixel Packing When Video Format Bridge is Not
> Present"
> > > >
> > > > So the driver is currently made to load only in case VFB is enabled.
> > >
> > > I understand that the driver doesn't support the case where the VFB
> > > is disabled, but the DT bindings shouldn't care about that. The
> > > document of
> > > v4.1 of the subsystem states that the width of the video_out port is
> > > then selected under "CSI-2 Options TDATA width" (page 11). I however
> > > don't such such an option described on pages 55 or 56, but there's
> > > an AXIS_TDATA_WIDTH parameter on page 61.
> > >
> > > Is the pixel format relevant when the VFB is disabled ?
> >
> > When the VFB is disabled, all supported data types will be allowed i.e. no
> filtering will occur.
> > But the data output will be in 32/64 bit TDATA width (no dependence on
> > pixels per clock) and will adhere to the "Recommended Memory Storage"
> section of the CSI spec.
> > In this case data being sent on the bus won't compare to what media bus
> format documentation describes.
> 
> My understanding is that, in the case xlnx,vfb would be absent (not supported
> in the driver yet), the xlnx,csi-pxl-format should not be set ? If that's correct, I'd
> like to capture that in the bindings already.

That is correct. xlnx,csi-pxl-format is absent when xlnx,vfb is absent.

> It could be expressed by dropping xlnx,csi-pxl-format from the required
> section, and adding
> 
> if:
>   required:
>     - xlnx,vfb
> then:
>   required:
>     - xlnx,csi-pxl-format
> else:
>   properties:
>     xlnx,csi-pxl-format: false
> 
> As you will have two conditions defined, they should be grouped with
> 
> allOf:
>   - if:
>       required:
>         - xlnx,vfb
>     then:
>       required:
>         - xlnx,csi-pxl-format
>     else:
>       properties:
>         xlnx,csi-pxl-format: false
> 
>   - if:
>       not:
>         required:
>           - xlnx,en-csi-v2-0
>     then:
>       properties:
>         xlnx,en-vcx: false
> 

Thanks for sharing on how to add this condition in YAML.
I will update this in the next version.

> > > > +
> > > > +  xlnx,vfb:
> > > > +    type: boolean
> > > > +    description: Present when Video Format Bridge is enabled in
> > > > + IP configuration
> > > > +
> > > > +  xlnx,en-csi-v2-0:
> > > > +    type: boolean
> > > > +    description: Present if CSI v2 is enabled in IP configuration.
> > > > +
> > > > +  xlnx,en-vcx:
> > > > +    type: boolean
> > > > +    description: |
> > > > +      When present, there are maximum 16 virtual channels, else
> > > > +      only 4. This is present only if xlnx,en-csi-v2-0 is present.
> > >
> > > The last sentence should be removed, and replaced with
> > >
> > > if:
> > >   not:
> > >     required:
> > >       - xlnx,en-csi-v2-0
> > > then:
> > >   properties:
> > >     xlnx,en-vcx: false
> > >
> > > (to be placed after required: and before additionalProperties:).
> >
> > Got it. Thanks for the tips on YAML.
> > I will update this in next version.
> >
> > > > +
> > > > +  xlnx,en-active-lanes:
> > > > +    type: boolean
> > > > +    description: |
> > > > +      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.
> > > > +
> > > > +  video-reset-gpios:
> > > > +    description: Optional specifier for a GPIO that asserts video_aresetn.
> > > > +    maxItems: 1
> > > > +
> > > > +  ports:
> > > > +    type: object
> > > > +
> > > > +    properties:
> > > > +      port@0:
> > > > +        type: object
> > > > +        description: |
> > > > +          Input / sink port node, single endpoint describing the
> > > > +          CSI-2 transmitter.
> > > > +
> > > > +        properties:
> > > > +          reg:
> > > > +            const: 0
> > > > +
> > > > +          endpoint:
> > > > +            type: object
> > > > +
> > > > +            properties:
> > > > +
> > > > +              data-lanes:
> > > > +                description: |
> > > > +                  This is required only in the sink port 0 endpoint which
> > > > +                  connects to MIPI CSI-2 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.
> > > > +                items:
> > > > +                  - const: 1
> > > > +                  - const: 2
> > > > +                  - const: 3
> > > > +                  - const: 4
> > > > +
> > > > +              remote-endpoint: true
> > > > +
> > > > +            required:
> > > > +              - data-lanes
> > > > +              - remote-endpoint
> > > > +
> > > > +            additionalProperties: false
> > > > +
> > > > +        additionalProperties: false
> > > > +
> > > > +      port@1:
> > > > +        type: object
> > > > +        description: |
> > > > +          Output / source port node, endpoint describing modules
> > > > +          connected the CSI-2 receiver.
> > > > +
> > > > +        properties:
> > > > +
> > > > +          reg:
> > > > +            const: 1
> > > > +
> > > > +          endpoint:
> > > > +            type: object
> > > > +
> > > > +            properties:
> > > > +
> > > > +              remote-endpoint: true
> > > > +
> > > > +            required:
> > > > +              - remote-endpoint
> > > > +
> > > > +            additionalProperties: false
> > > > +
> > > > +        additionalProperties: false
> > > > +
> > > > +required:
> > > > +  - compatible
> > > > +  - reg
> > > > +  - interrupts
> > > > +  - clocks
> > > > +  - clock-names
> > > > +  - xlnx,csi-pxl-format
> > > > +  - ports
> > > > +
> > > > +additionalProperties: false
> > > > +
> > > > +examples:
> > > > +  - |
> > > > +    #include <dt-bindings/gpio/gpio.h>
> > > > +    xcsi2rxss_1: csi2rx@...20000 {
> > > > +        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>;
> > > > +        video-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 CSI-2 Camera handle */
> > > > +                    remote-endpoint = <&camera_out>;
> > > > +                };
> > > > +            };
> > > > +            port@1 {
> > > > +                /* Source port */
> > > > +                reg = <1>;
> > > > +                csiss_out: endpoint {
> > > > +                    remote-endpoint = <&vproc_in>;
> > > > +                };
> > > > +            };
> > > > +        };
> > > > +    };
> 
> --
> Regards,
> 
> Laurent Pinchart

Regards
Vishal Sagar

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