RE: [PATCH v13 1/2] media: dt-bindings: media: xilinx: Add Xilinx MIPI CSI-2 Rx Subsystem

Vishal Sagar
2020-05-27T14:16:30Z

Hi Laurent,

> -----Original Message-----
> From: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> Sent: Wednesday, May 27, 2020 6:54 PM
> To: Vishal Sagar <vsagar@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>; Rob Herring
> <robh@kernel.org>
> Subject: Re: [PATCH v13 1/2] media: dt-bindings: media: xilinx: Add Xilinx MIPI
> CSI-2 Rx Subsystem
>
> Hi Vishal,
>
> On Wed, May 27, 2020 at 11:53:01AM +0000, Vishal Sagar wrote:
> > On Sunday, May 24, 2020 7:32 AM, Laurent Pinchart wrote:
> > > On Tue, May 12, 2020 at 08:49:46PM +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@xilinx.com>
> > > > Reviewed-by: Hyun Kwon <hyun.kwon@xilinx.com>
> > > > Reviewed-by: Rob Herring <robh@kernel.org>
> > > > Reviewed-by: Luca Ceresoli <luca@lucaceresoli.net>
> > > > Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> > > > ---
> > > > v13
> > > > - Based on Laurent's suggestions
> > > > - Fixed the datatypes values as minimum and maximum
> > > > - condition added for en-vcx property
> > > >
> > > > 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 | 226
> > > > ++++++++++++++++++
> > > > 1 file changed, 226 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..b0885f461785
> > > > --- /dev/null
> > > > +++ b/Documentation/devicetree/bindings/media/xilinx/xlnx,csi2rxss
> > > > +++ .yam
> > > > +++ l
> > > > @@ -0,0 +1,226 @@
> > > > +# 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@xilinx.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.
> > > > +
> > > > +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
> > > > + - anyOf:
> > > > + - minimum: 0x1e
> > > > + - maximum: 0x24
> > > > + - minimum: 0x28
> > > > + - maximum: 0x2f
> > > > +
> > > > + 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.
> > > > +
> > > > + 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
> > > > +
> > > > +if:
> > > > + not:
> > > > + required:
> > > > + - xlnx,en-csi-v2-0
> > > > +then:
> > > > + properties:
> > > > + xlnx,en-vcx: false
> > >
> > > As I've just commented on v12, I think we should condition the
> > > xlnx,csi-pxl- format property to xlnx,vfb being set.
> > > xlnx,csi-pxl-format should be removed from the required properties above,
> and the following conditions added:
> > >
> > > 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
> > >
> > > The 'allOf' is needed as you can't have two 'if' constructs at the top level.
> > >
> > Thanks for sharing the explanation for this.
> > Can you please share where I can get this info?
>
> The json-schema specification is available at https://json-
> schema.org/specification.html. allOf is defined in https://json-
> schema.org/draft/2019-09/json-schema-core.html#allOf.
>
> JSON schemas are expressed in JSON format, and YAML is a (more readable)
> superset syntax of JSON. A YAML document contains lists and objects:
>
> - this
> - is
> - a
> - list
>
> object:
> can: have
> properties:
> that: can
> be: other
> objects
>
> An object is similar to a Python dictionary, it can't have multiple entries with
> the same key. So having
>
> 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
>
> at the top level is not valid, the same way that
>
> properties:
> reg:
> maxItems: 1
> reg:
> maxItems: 1
>
> wouldn't be valid. The allOf object has a value that is a list of
> schemas:
>
> allOf:
> - schema1
> - schema2
> - schema3
>
> and in this case, we use it with a if...then...else for each of the schemas. As
> documented in the spec, "An instance validates successfully against [allOf] if it
> validates successfully against all schemas defined by [allOf]'s value".
>
> allOf is also used to include sub-schemas, as explained in
> Documentation/devicetree/bindings/example-schema.yaml.
>
> vendor,int-property:
> description: Vendor specific properties must have a description
> # 'allOf' is the json-schema way of subclassing a schema. Here the base
> # type schema is referenced and then additional constraints on the values
> # are added.
> allOf:
> - $ref: /schemas/types.yaml#/definitions/uint32
> - enum: [2, 4, 6, 8, 10]
>
> If this was written
>
> vendor,int-property:
> $ref: /schemas/types.yaml#/definitions/uint32
> enum: [2, 4, 6, 8, 10]
>
> we would have an issue (among other problems) if
> /schemas/types.yaml#/definitions/uint32 contained an enum, as there would
> be two enum properties for vendor,int-property.
>

Thanks for the detailed explanation Laurent!

> > > Please however let me know if my understanding is wrong and
> > > xlnx,csi-pxl- format is needed even when xlnx,vfb is not set. In
> > > that case please ignore this change (but please add the ... below).
> >
> > Ok. I will add ... in the end.
> >
> > > > +
> > > > +additionalProperties: false
> > > > +
> > > > +examples:
> > > > + - |
> > > > + #include <dt-bindings/gpio/gpio.h>
> > > > + 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>;
> > > > + 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>;
> > > > + };
> > > > + };
> > > > + };
> > > > + };
> > >
> > > YAML files usually end with
> > >
> > > ...
> > >
> > > on the last line to mark the end of file.
> > >
> >
> > Ok I will add this to the end of the file.
> >
> > > Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
>
> --
> Regards,
>
> Laurent Pinchart

Regards
Vishal Sagar