[PATCH v2 61/66] dt-bindings: media: Add Allwinner A31 ISP bindings documentation

[Paul Kocialkowski]

Hi Laurent,

Thanks for the review and the follow-up questions!

On Mon 07 Feb 22, 17:51, Laurent Pinchart wrote:
> Hi Paul,
> 
> Thank you for the patch.
> 
> On Sat, Feb 05, 2022 at 07:54:24PM +0100, Paul Kocialkowski wrote:
> > This introduces YAML bindings documentation for the Allwinner A31 Image
> > Signal Processor (ISP).
> > 
> > Signed-off-by: Paul Kocialkowski <paul.kocialkowski at bootlin.com>
> > ---
> >  .../media/allwinner,sun6i-a31-isp.yaml        | 117 ++++++++++++++++++
> >  1 file changed, 117 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/media/allwinner,sun6i-a31-isp.yaml
> > 
> > diff --git a/Documentation/devicetree/bindings/media/allwinner,sun6i-a31-isp.yaml b/Documentation/devicetree/bindings/media/allwinner,sun6i-a31-isp.yaml
> > new file mode 100644
> > index 000000000000..2d87022c43ce
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/media/allwinner,sun6i-a31-isp.yaml
> > @@ -0,0 +1,117 @@
> > +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/media/allwinner,sun6i-a31-isp.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: Allwinner A31 Image Signal Processor Driver (ISP) Device Tree Bindings
> > +
> > +maintainers:
> > +  - Paul Kocialkowski <paul.kocialkowski at bootlin.com>
> > +
> > +properties:
> > +  compatible:
> > +    enum:
> > +      - allwinner,sun6i-a31-isp
> > +      - allwinner,sun8i-v3s-isp
> > +
> > +  reg:
> > +    maxItems: 1
> > +
> > +  interrupts:
> > +    maxItems: 1
> > +
> > +  clocks:
> > +    items:
> > +      - description: Bus Clock
> > +      - description: Module Clock
> > +      - description: DRAM Clock
> 
> That's interesting, does the ISP have a dedicated DRAM ?

It doesn't, it actually uses the main DRAM with the "mbus" interconnect.
The clock is probably for the DMA engine.

> > +
> > +  clock-names:
> > +    items:
> > +      - const: bus
> > +      - const: mod
> > +      - const: ram
> > +
> > +  resets:
> > +    maxItems: 1
> > +
> > +  ports:
> > +    $ref: /schemas/graph.yaml#/properties/ports
> > +
> > +    properties:
> > +      port at 0:
> > +        $ref: /schemas/graph.yaml#/$defs/port-base
> > +        description: CSI0 input port
> > +
> > +        properties:
> > +          reg:
> > +            const: 0
> > +
> > +          endpoint:
> > +            $ref: video-interfaces.yaml#
> > +            unevaluatedProperties: false
> 
> If no other property than remote-endpoint are allowed, I'd write
> 
>           endpoint:
>             $ref: video-interfaces.yaml#
> 	    remote-endpoint: true
>             additionalProperties: false
> 
> Same below.
> 
> > +
> > +        additionalProperties: false
> > +
> > +      port at 1:
> > +        $ref: /schemas/graph.yaml#/$defs/port-base
> > +        description: CSI1 input port
> > +
> > +        properties:
> > +          reg:
> > +            const: 0
> 
> This should be 1.

Correct, thanks!

> > +
> > +          endpoint:
> > +            $ref: video-interfaces.yaml#
> > +            unevaluatedProperties: false
> > +
> > +        additionalProperties: false
> > +
> > +    anyOf:
> > +      - required:
> > +        - port at 0
> > +      - required:
> > +        - port at 1
> 
> As ports are an intrinsic property of the ISP, both should be required,
> but they don't have to be connected.

Well the ISP does have the ability to source from either CSI0 and CSI1
but I don't really get the point of declaring both ports when only one
of the two controllers is present.

> By the way, how do you select at runtime which CSI-2 RX the ISP gets its
> image stream from ? Is it configured through registers of the ISP ?

Actually what the ISP gets is fully dependent on what is received by the
CSI controller it is connected to (which can be the mipi csi-2 controller
or its direct parallel pins), so the configuration happens on the CSI side.

Thanks,

Paul

> > +
> > +required:
> > +  - compatible
> > +  - reg
> > +  - interrupts
> > +  - clocks
> > +  - clock-names
> > +  - resets
> > +
> > +additionalProperties: false
> > +
> > +examples:
> > +  - |
> > +    #include <dt-bindings/interrupt-controller/arm-gic.h>
> > +    #include <dt-bindings/clock/sun8i-v3s-ccu.h>
> > +    #include <dt-bindings/reset/sun8i-v3s-ccu.h>
> > +
> > +    isp: isp at 1cb8000 {
> > +        compatible = "allwinner,sun8i-v3s-isp";
> > +        reg = <0x01cb8000 0x1000>;
> > +        interrupts = <GIC_SPI 83 IRQ_TYPE_LEVEL_HIGH>;
> > +        clocks = <&ccu CLK_BUS_CSI>,
> > +             <&ccu CLK_CSI1_SCLK>,
> > +             <&ccu CLK_DRAM_CSI>;
> > +        clock-names = "bus", "mod", "ram";
> > +        resets = <&ccu RST_BUS_CSI>;
> > +
> > +        ports {
> > +            #address-cells = <1>;
> > +            #size-cells = <0>;
> > +
> > +            port at 0 {
> > +                reg = <0>;
> > +
> > +                isp_in_csi0: endpoint {
> > +                    remote-endpoint = <&csi0_out_isp>;
> > +                };
> > +            };
> > +        };
> > +    };
> > +
> > +...
> 
> -- 
> Regards,
> 
> Laurent Pinchart

-- 
Paul Kocialkowski, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com
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