Re: [PATCH v6 5/8] dt-bindings: media: add TI DS90UB960 FPD-Link III Deserializer

Tomi Valkeinen
2023-01-09T09:55:26Z

On 09/01/2023 11:09, Laurent Pinchart wrote:
> On Mon, Jan 09, 2023 at 10:30:13AM +0200, Tomi Valkeinen wrote:
>> On 08/01/2023 05:23, Laurent Pinchart wrote:
>>> Hi Tomi,
>>>
>>> Thank you for the patch.
>>>
>>> On Thu, Jan 05, 2023 at 04:03:04PM +0200, Tomi Valkeinen wrote:
>>>> Add DT bindings for TI DS90UB960 FPD-Link III Deserializer.
>>>>
>>>> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
>>>> Reviewed-by: Rob Herring <robh@kernel.org>
>>>> ---
>>>> .../bindings/media/i2c/ti,ds90ub960.yaml | 402 ++++++++++++++++++
>>>> 1 file changed, 402 insertions(+)
>>>> create mode 100644 Documentation/devicetree/bindings/media/i2c/ti,ds90ub960.yaml
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/media/i2c/ti,ds90ub960.yaml b/Documentation/devicetree/bindings/media/i2c/ti,ds90ub960.yaml
>>>> new file mode 100644
>>>> index 000000000000..664799ae55be
>>>> --- /dev/null
>>>> +++ b/Documentation/devicetree/bindings/media/i2c/ti,ds90ub960.yaml
>>>> @@ -0,0 +1,402 @@
>>>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>>>> +%YAML 1.2
>>>> +---
>>>> +$id: http://devicetree.org/schemas/media/i2c/ti,ds90ub960.yaml#
>>>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>>>> +
>>>> +title: Texas Instruments DS90UB9XX Family FPD-Link Deserializer Hubs
>>>> +
>>>> +maintainers:
>>>> + - Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
>>>> +
>>>> +description:
>>>> + The TI DS90UB9XX devices are FPD-Link video deserializers with I2C and GPIO
>>>> + forwarding.
>>>> +
>>>> +properties:
>>>> + compatible:
>>>> + enum:
>>>> + - ti,ds90ub960-q1
>>>> + - ti,ds90ub9702-q1
>>>> +
>>>> + reg:
>>>> + maxItems: 1
>>>> +
>>>> + clocks:
>>>> + maxItems: 1
>>>> + description:
>>>> + Reference clock connected to the REFCLK pin.
>>>> +
>>>> + clock-names:
>>>> + items:
>>>> + - const: refclk
>>>> +
>>>> + powerdown-gpios:
>>>> + maxItems: 1
>>>> + description:
>>>> + Specifier for the GPIO connected to the PDB pin.
>>>> +
>>>> + i2c-alias-pool:
>>>> + $ref: /schemas/types.yaml#/definitions/uint16-array
>>>> + description:
>>>> + I2C alias pool is a pool of I2C addresses on the main I2C bus that can be
>>>> + used to access the remote peripherals on the serializer's I2C bus. The
>>>> + addresses must be available, not used by any other peripheral. Each
>>>> + remote peripheral is assigned an alias from the pool, and transactions to
>>>> + that address will be forwarded to the remote peripheral, with the address
>>>> + translated to the remote peripheral's real address. This property is not
>>>> + needed if there are no I2C addressable remote peripherals.
>>>> +
>>>> + links:
>>>> + type: object
>>>> + additionalProperties: false
>>>> +
>>>> + properties:
>>>> + '#address-cells':
>>>> + const: 1
>>>> +
>>>> + '#size-cells':
>>>> + const: 0
>>>> +
>>>> + ti,manual-strobe:
>>>> + type: boolean
>>>> + description:
>>>> + Enable manual strobe position and EQ level
>>>> +
>>>> + patternProperties:
>>>> + '^link@[0-3]$':
>>>> + type: object
>>>> + additionalProperties: false
>>>> + properties:
>>>> + reg:
>>>> + description: The link number
>>>> + maxItems: 1
>>>> +
>>>> + i2c-alias:
>>>> + description:
>>>> + The I2C address used for the serializer. Transactions to this
>>>> + address on the I2C bus where the deserializer resides are
>>>> + forwarded to the serializer.
>>>> +
>>>> + ti,rx-mode:
>>>> + $ref: /schemas/types.yaml#/definitions/uint32
>>>> + enum:
>>>> + - 0 # RAW10
>>>> + - 1 # RAW12 HF
>>>> + - 2 # RAW12 LF
>>>> + - 3 # CSI2 SYNC
>>>> + - 4 # CSI2 NON-SYNC
>>>> + description:
>>>> + FPD-Link Input Mode. This should reflect the hardware and the
>>>> + default mode of the connected camera module.
>>>
>>> As the remote device may not be a camera, I'd write "of the connected
>>> device" or "of the connected serializer".
>>
>> I was trying to include the sensor also in the "camera module", as the
>> sensor's "normal" pixel cloud would affect RAW modes (HF/LF). Perhaps
>> "connected device" covers this.
>>
>>>> +
>>>> + ti,cdr-mode:
>>>> + $ref: /schemas/types.yaml#/definitions/uint32
>>>> + enum:
>>>> + - 0 # FPD-Link III
>>>> + - 1 # FPD-Link IV
>>>> + description:
>>>> + FPD-Link CDR Mode. This should reflect the hardware and the
>>>> + default mode of the connected camera module.
>>>> +
>>>> + ti,strobe-pos:
>>>> + $ref: /schemas/types.yaml#/definitions/int32
>>>> + minimum: -13
>>>> + maximum: 13
>>>> + description: Manual strobe position
>>>> +
>>>> + ti,eq-level:
>>>> + $ref: /schemas/types.yaml#/definitions/uint32
>>>> + maximum: 14
>>>> + description: Manual EQ level
>>>> +
>>>> + serializer:
>>>> + type: object
>>>> + description: FPD-Link Serializer node
>>>> +
>>>> + required:
>>>> + - reg
>>>> + - i2c-alias
>>>> + - ti,rx-mode
>>>> + - serializer
>>>> +
>>>> + ports:
>>>> + $ref: /schemas/graph.yaml#/properties/ports
>>>> +
>>>> + properties:
>>>> + port@0:
>>>> + $ref: /schemas/graph.yaml#/$defs/port-base
>>>> + unevaluatedProperties: false
>>>> + description: FPD-Link input 0
>>>> +
>>>> + properties:
>>>> + endpoint:
>>>> + $ref: /schemas/media/video-interfaces.yaml#
>>>> + unevaluatedProperties: false
>>>> + description:
>>>> + Endpoint for FPD-Link port. If the RX mode for this port is RAW,
>>>> + hsync-active and vsync-active must be defined.
>>>> +
>>>> + port@1:
>>>> + $ref: /schemas/graph.yaml#/$defs/port-base
>>>> + unevaluatedProperties: false
>>>> + description: FPD-Link input 1
>>>> +
>>>> + properties:
>>>> + endpoint:
>>>> + $ref: /schemas/media/video-interfaces.yaml#
>>>> + unevaluatedProperties: false
>>>> + description:
>>>> + Endpoint for FPD-Link port. If the RX mode for this port is RAW,
>>>> + hsync-active and vsync-active must be defined.
>>>> +
>>>> + port@2:
>>>> + $ref: /schemas/graph.yaml#/$defs/port-base
>>>> + unevaluatedProperties: false
>>>> + description: FPD-Link input 2
>>>> +
>>>> + properties:
>>>> + endpoint:
>>>> + $ref: /schemas/media/video-interfaces.yaml#
>>>> + unevaluatedProperties: false
>>>> + description:
>>>> + Endpoint for FPD-Link port. If the RX mode for this port is RAW,
>>>> + hsync-active and vsync-active must be defined.
>>>> +
>>>> + port@3:
>>>> + $ref: /schemas/graph.yaml#/$defs/port-base
>>>> + unevaluatedProperties: false
>>>> + description: FPD-Link input 3
>>>> +
>>>> + properties:
>>>> + endpoint:
>>>> + $ref: /schemas/media/video-interfaces.yaml#
>>>> + unevaluatedProperties: false
>>>> + description:
>>>> + Endpoint for FPD-Link port. If the RX mode for this port is RAW,
>>>> + hsync-active and vsync-active must be defined.
>>>> +
>>>> + port@4:
>>>> + $ref: /schemas/graph.yaml#/$defs/port-base
>>>> + unevaluatedProperties: false
>>>> + description: CSI-2 Output 0
>>>> +
>>>> + properties:
>>>> + endpoint:
>>>> + $ref: /schemas/media/video-interfaces.yaml#
>>>> + unevaluatedProperties: false
>>>> +
>>>> + properties:
>>>> + data-lanes:
>>>> + minItems: 1
>>>> + maxItems: 4
>>>> +
>>>> + required:
>>>> + - data-lanes
>>>> +
>>>> + port@5:
>>>> + $ref: /schemas/graph.yaml#/$defs/port-base
>>>> + unevaluatedProperties: false
>>>> + description: CSI-2 Output 1
>>>> +
>>>> + properties:
>>>> + endpoint:
>>>> + $ref: /schemas/media/video-interfaces.yaml#
>>>> + unevaluatedProperties: false
>>>> +
>>>> + properties:
>>>> + data-lanes:
>>>> + minItems: 1
>>>> + maxItems: 4
>>>> +
>>>> + required:
>>>> + - data-lanes
>>>
>>> I think you need
>>>
>>> required:
>>> - port@0
>>> - port@1
>>> - port@2
>>> - port@3
>>> - port@4
>>> - port@5
>>
>> Is that needed? I think often some of the ports are unused (e.g. the
>> example in this yaml file). Is it customary to still require empty port
>> nodes in the DT?
>
> Ports are an intrinsic property of a device, they don't depend on the
> device integration in the system. In this case, the UB960 has four
> FPD-Link inputs and two CSI-2 outputs, that's a property of the chip.
> They don't have to be connected to anything on the board, so endpooints
> are optional.

Yes, but why do they have to be required? A missing port node implies
that it's not used, doesn't it? I don't mind much, it just feels a bit
extra to add multiple almost empty "port@X { reg = <X>; };" style nodes
to the dts file.

Tomi