Re: [PATCH 2/4] dt-bindings: display: ti: Add schema for AM625 OLDI Transmitter

[Aradhya Bhatia]

Hi Laurent,

Thank you for reviewing the patches!

On 13-May-24 01:04, Laurent Pinchart wrote:
> Hi Aradhya,
> 
> Thank you for the patch.
> 
> On Sun, May 12, 2024 at 01:00:53AM +0530, Aradhya Bhatia wrote:
>> Add devicetree binding schema for AM625 OLDI Transmitters.
>>
>> Signed-off-by: Aradhya Bhatia <a-bhatia1@xxxxxx>
>> ---
>>  .../bindings/display/ti/ti,am625-oldi.yaml    | 153 ++++++++++++++++++
>>  MAINTAINERS                                   |   1 +
>>  2 files changed, 154 insertions(+)
>>  create mode 100644 Documentation/devicetree/bindings/display/ti/ti,am625-oldi.yaml
>>
>> diff --git a/Documentation/devicetree/bindings/display/ti/ti,am625-oldi.yaml b/Documentation/devicetree/bindings/display/ti/ti,am625-oldi.yaml
>> new file mode 100644
>> index 000000000000..0a96e600bc0b
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/display/ti/ti,am625-oldi.yaml
>> @@ -0,0 +1,153 @@
>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>> +%YAML 1.2
>> +---
>> +$id: http://devicetree.org/schemas/display/ti/ti,am625-oldi.yaml#
>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>> +
>> +title: Texas Instruments AM625 OLDI Transmitter
>> +
>> +maintainers:
>> +  - Tomi Valkeinen <tomi.valkeinen@xxxxxxxxxxxxxxxx>
>> +  - Aradhya Bhatia <a-bhatia1@xxxxxx>
>> +
>> +description: |
>> +  The AM625 TI Keystone OpenLDI transmitter (OLDI TX) supports serialized RGB
>> +  pixel data transmission between host and flat panel display over LVDS (Low
>> +  Voltage Differential Sampling) interface. The OLDI TX consists of 7-to-1 data
>> +  serializers, and 4-data and 1-clock LVDS outputs. It supports the LVDS output
>> +  formats "jeida-18", "jeida-24" and "vesa-18", and can accept 24-bit RGB or
>> +  padded and un-padded 18-bit RGB bus formats as input.
>> +
>> +properties:
>> +  reg:
>> +    maxItems: 1
>> +
>> +  clocks:
>> +    maxItems: 1
>> +    description: serial clock input for the OLDI transmitters
>> +
>> +  clock-names:
>> +    const: s_clk
>> +
>> +  ti,companion-oldi:
>> +    $ref: /schemas/types.yaml#/definitions/phandle
>> +    description:
>> +      phandle to companion OLDI transmitter. This property is mandatory for the
>> +      primarty OLDI TX if the OLDI TXes are expected to work either in dual-lvds
>> +      mode or in clone mode. This property should point to the secondary OLDI
>> +      TX.
>> +
>> +  ti,secondary-oldi:
>> +    type: boolean
>> +    description: Boolean property to mark an OLDI TX as secondary node.
>> +
>> +  ti,oldi-io-ctrl:
>> +    $ref: /schemas/types.yaml#/definitions/phandle
>> +    description:
>> +      phandle to syscon device node mapping OLDI IO_CTRL registers found in the
>> +      control MMR region. This property is needed for OLDI interface to work.
>> +
>> +  ports:
>> +    $ref: /schemas/graph.yaml#/properties/ports
>> +
>> +    properties:
>> +      port@0:
>> +        $ref: /schemas/graph.yaml#/properties/port
>> +        description: Parallel RGB input port
>> +
>> +      port@1:
>> +        $ref: /schemas/graph.yaml#/properties/port
>> +        description: LVDS output port
>> +
>> +    required:
>> +      - port@0
>> +      - port@1
>> +
>> +allOf:
>> +  - if:
>> +      properties:
>> +        ti,secondary-oldi: true
>> +    then:
>> +      properties:
>> +        ti,companion-oldi: false
>> +        ti,oldi-io-ctrl: false
>> +        clocks: false
>> +        clock-names: false
>> +
>> +    else:
>> +      required:
>> +        - ti,oldi-io-ctrl
>> +        - clocks
>> +        - clock-names
>> +
>> +required:
>> +  - reg
>> +  - ports
>> +
>> +additionalProperties: false
>> +
>> +examples:
>> +  - |
>> +    #include <dt-bindings/soc/ti,sci_pm_domain.h>
>> +
>> +    oldi_txes {
>> +        #address-cells = <1>;
>> +        #size-cells = <0>;
>> +        oldi: oldi@0 {
>> +            reg = <0>;
>> +            clocks = <&k3_clks 186 0>;
>> +            clock-names = "s_clk";
>> +            ti,oldi-io-ctrl = <&dss_oldi_io_ctrl>;
> 
> What bus does this device live on ? Couldn't the I/O register space be
> referenced by the reg property ?.
> 

These registers are a part of the system-controller register space
(ctrl_mmr0). The whole register set is owned by the main_conf[0]
devicetree node, with sub-nodes pointing to specific regions. That's why
I cannot reference these registers directly.

The IO control node for OLDI will look like this though[1].

[0]:
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/arch/arm64/boot/dts/ti/k3-am62-main.dtsi#n45

[1]:
https://github.com/aradhya07/linux-ab/commit/7d7184fb36dc22c67cc2704fe708e885f300860c


>> +            ports {
>> +                #address-cells = <1>;
>> +                #size-cells = <0>;
>> +                port@0 {
>> +                    reg = <0>;
>> +                    oldi_in: endpoint {
>> +                        remote-endpoint = <&dpi0_out>;
>> +                    };
>> +                };
>> +            };
>> +        };
>> +    };
>> +
> 

[ ... ]

-- 
Regards
Aradhya