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

Laurent Pinchart
2020-05-27T13:24:18Z

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.yaml
> > > b/Documentation/devicetree/bindings/media/xilinx/xlnx,csi2rxss.yaml
> > > 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.

> > 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